Javascript（计数 < elements.length）不起作用
Javascript (count < elements.length) doesnt work
我正在尝试使用 ctrl+f 进行搜索。我有一个功能，可以在您按下回车键时滚动到下一个关键字。我试图让它在你读完所有单词后重置计数，但它只是给我一个错误。例如，如果我搜索“Lorem”，它将 return 13 个匹配项，因此在我第 13 次按回车后它应该会重置，但它却给我一个错误。我不明白为什么 (count < elements.length) 不起作用。这是我卡住的部分：
P.S。为避免混淆，“mark”是一个自定义元素标签，它被包装到与输入匹配的文本中的单词上，然后突出显示它。
//scroll to searched keyword
if (e.key === 'Enter') {
var elements = document.getElementsByTagName("mark");
if (count < elements.length) {
window.scroll({top: elements[++count].offsetTop, behavior: 'smooth'})
} else {
count = 0;
window.scroll({top: elements[0].offsetTop, behavior: 'smooth'});
}
console.log("length " + elements.length);
} else {
count = 0;
var element = document.getElementsByTagName("mark")[0];
if(element){
window.scroll({top: element.offsetTop, behavior: 'smooth'});
}
}
console.log(count);
// Original JavaScript code by Chirp Internet: chirpinternet.eu
// Please acknowledge use of this code by including this header.
function Hilitor(id, tag)
{
// private variables
var targetNode = document.getElementById("txt")
var hiliteTag = tag || "MARK";
var skipTags = new RegExp("^(?:" + hiliteTag + "|SCRIPT|FORM|SPAN)$");
// var colors = ["#ff6", "#a0ffff", "#9f9", "#f99", "#f6f"];
var colors = ["#aac42a", "#80bd01", "#33a643"];
var wordColor = [];
var colorIdx = 0;
var matchRegExp = "";
var openLeft = false;
var openRight = false;
// characters to strip from start and end of the input string
var endRegExp = new RegExp('^[^\w]+|[^\w]+$', "g");
// characters used to break up the input string into words
var breakRegExp = new RegExp('[^\w\'-]+', "g");
this.setEndRegExp = function(regex) {
endRegExp = regex;
return endRegExp;
};
this.setBreakRegExp = function(regex) {
breakRegExp = regex;
return breakRegExp;
};
this.setMatchType = function(type)
{
switch(type)
{
case "left":
this.openLeft = false;
this.openRight = true;
break;
case "right":
this.openLeft = true;
this.openRight = false;
break;
case "open":
this.openLeft = this.openRight = true;
break;
default:
this.openLeft = this.openRight = false;
}
};
this.setRegex = function(input)
{
input = input.replace(endRegExp, "");
input = input.replace(breakRegExp, "|");
input = input.replace(/^\||\|$/g, "");
if(input) {
var re = "(" + input + ")";
if(!this.openLeft) {
re = "\b" + re;
}
if(!this.openRight) {
re = re + "\b";
}
matchRegExp = new RegExp(re, "i");
return matchRegExp;
}
return false;
};
this.getRegex = function()
{
var retval = matchRegExp.toString();
retval = retval.replace(/(^\/(\b)?|\(|\)|(\b)?\/i$)/g, "");
retval = retval.replace(/\|/g, " ");
return retval;
};
// recursively apply word highlighting
this.hiliteWords = function(node)
{
if(node === undefined || !node) return;
if(!matchRegExp) return;
if(skipTags.test(node.nodeName)) return;
if(node.hasChildNodes()) {
for(var i=0; i < node.childNodes.length; i++)
this.hiliteWords(node.childNodes[i]);
}
if(node.nodeType == 3) { // NODE_TEXT
if((nv = node.nodeValue) && (regs = matchRegExp.exec(nv))) {
if(!wordColor[regs[0].toLowerCase()]) {
wordColor[regs[0].toLowerCase()] = colors[colorIdx++ % colors.length];
}
var match = document.createElement(hiliteTag);
match.appendChild(document.createTextNode(regs[0]));
match.style.backgroundColor = wordColor[regs[0].toLowerCase()];
match.style.color = "#000";
var after = node.splitText(regs.index);
after.nodeValue = after.nodeValue.substring(regs[0].length);
node.parentNode.insertBefore(match, after);
}
};
};
// remove highlighting
this.remove = function()
{
var arr = document.getElementsByTagName(hiliteTag);
while(arr.length && (el = arr[0])) {
var parent = el.parentNode;
parent.replaceChild(el.firstChild, el);
parent.normalize();
}
};
// start highlighting at target node
this.apply = function(input)
{
this.remove();
if(input === undefined || !(input = input.replace(/(^\s+|\s+$)/g, ""))) {
return;
}
if(this.setRegex(input)) {
this.hiliteWords(targetNode);
}
return matchRegExp;
};
}
<!-- Search field -->
<input type="text" id="keywords" placeholder="Search on the page..."></input>
<div id="txt"><div class="faq-question"><h4>What is Lorem Ipsum?</h4>
<p>Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book. It has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged. It was popularised in the 1960s with the release of Letraset sheets containing Lorem Ipsum passages, and more recently with desktop publishing software like Aldus PageMaker including versions of Lorem Ipsum.</p></div>
<div class="faq-question"><h4>Why do we use it?</h4>
<p>It is a long established fact that a reader will be distracted by the readable content of a page when looking at its layout. The point of using Lorem Ipsum is that it has a more-or-less normal distribution of letters, as opposed to using 'Content here, content here', making it look like readable English. Many desktop publishing packages and web page editors now use Lorem Ipsum as their default model text, and a search for 'lorem ipsum' will uncover many web sites still in their infancy. Various versions have evolved over the years, sometimes by accident, sometimes on purpose (injected humour and the like).</p></div>
<div class="faq-question"><h4>Where does it come from?</h4>
<p>Contrary to popular belief, Lorem Ipsum is not simply random text. It has roots in a piece of classical Latin literature from 45 BC, making it over 2000 years old. Richard McClintock, a Latin professor at Hampden-Sydney College in Virginia, looked up one of the more obscure Latin words, consectetur, from a Lorem Ipsum passage, and going through the cites of the word in classical literature, discovered the undoubtable source. Lorem Ipsum comes from sections 1.10.32 and 1.10.33 of "de Finibus Bonorum et Malorum" (The Extremes of Good and Evil) by Cicero, written in 45 BC. This book is a treatise on the theory of ethics, very popular during the Renaissance. The first line of Lorem Ipsum, "Lorem ipsum dolor sit amet..", comes from a line in section 1.10.32.</p></div></div>
<style>
.sticky-faqsearch {position: sticky; top: 30px; box-shadow: 0px 5px 10px #4f4f5d29;}
</style>
<script type="text/javascript">
//highlight searched keyword
window.addEventListener("DOMContentLoaded", function(e) {
var myHilitor2 = new Hilitor("playground");
myHilitor2.setMatchType("left");
document.getElementById("keywords").addEventListener("keyup", function(e) {
myHilitor2.apply(this.value);
//Hide unrelated search results (hides faq-question with no matches to input)
var questions = document.getElementsByClassName("faq-question");
for(x = 0; x < questions.length; x++) {
if(questions[x].getElementsByTagName('mark').length){
questions[x].style.display = "block";
// console.log("input exists");
} else {
questions[x].style.display = "none";
// console.log("no matched keywords in this section");
}
//if page doesnt contain mark set display to block
if (document.getElementsByTagName('mark').length == 0) {
questions[x].style.display = "block";
// console.log("no input");
}
}
//scroll to searched keyword
var element = document.getElementsByTagName("mark")[0];
if(element){
window.scroll({top: element.offsetTop, behavior: 'smooth'});
}
////////////////////////////////////////////////////////////////////////
//scroll to searched keyword
if (e.key === 'Enter') {
var elements = document.getElementsByTagName("mark");
if (count < elements.length) {
window.scroll({top: elements[++count].offsetTop, behavior: 'smooth'})
} else {
count = 0;
window.scroll({top: elements[0].offsetTop, behavior: 'smooth'});
}
console.log("length " + elements.length);
} else {
count = 0;
var element = document.getElementsByTagName("mark")[0];
if(element){
window.scroll({top: element.offsetTop, behavior: 'smooth'});
}
}
console.log(count);
/////////////////////////////////////////////////////////////////////////
}, false);
}, false);
//search bar sticks to the top on scroll
window.onscroll = function() {seatchStickToTop()};
var faqsearch = document.getElementById("keywords");
var sticky = faqsearch.offsetTop;
function seatchStickToTop() {
if (window.pageYOffset > sticky) {
faqsearch.classList.add("sticky-faqsearch");
} else {
faqsearch.classList.remove("sticky-faqsearch");
}
}
</script>
让我们检查一下您的这部分代码：
if (count < elements.length) {
window.scroll({top: elements[++count].offsetTop, behavior: 'smooth'})
} else {
count = 0;
window.scroll({top: elements[0].offsetTop, behavior: 'smooth'});
}
count < elements.length时，你经过第一个分支。在那里，您使用 ++count，这意味着如果 count 最初是 elements.length - 1，您现在正试图访问超出范围的 elements[elements.length]，因此 undefined.
只需检查 if (count + 1 < elements.length) 就可以了，即“下一个元素还在列表中吗？”基本上。
我正在尝试使用 ctrl+f 进行搜索。我有一个功能，可以在您按下回车键时滚动到下一个关键字。我试图让它在你读完所有单词后重置计数，但它只是给我一个错误。例如，如果我搜索“Lorem”，它将 return 13 个匹配项，因此在我第 13 次按回车后它应该会重置，但它却给我一个错误。我不明白为什么 (count < elements.length) 不起作用。这是我卡住的部分：
P.S。为避免混淆，“mark”是一个自定义元素标签，它被包装到与输入匹配的文本中的单词上，然后突出显示它。
//scroll to searched keyword
if (e.key === 'Enter') {
var elements = document.getElementsByTagName("mark");
if (count < elements.length) {
window.scroll({top: elements[++count].offsetTop, behavior: 'smooth'})
} else {
count = 0;
window.scroll({top: elements[0].offsetTop, behavior: 'smooth'});
}
console.log("length " + elements.length);
} else {
count = 0;
var element = document.getElementsByTagName("mark")[0];
if(element){
window.scroll({top: element.offsetTop, behavior: 'smooth'});
}
}
console.log(count);
// Original JavaScript code by Chirp Internet: chirpinternet.eu
// Please acknowledge use of this code by including this header.
function Hilitor(id, tag)
{
// private variables
var targetNode = document.getElementById("txt")
var hiliteTag = tag || "MARK";
var skipTags = new RegExp("^(?:" + hiliteTag + "|SCRIPT|FORM|SPAN)$");
// var colors = ["#ff6", "#a0ffff", "#9f9", "#f99", "#f6f"];
var colors = ["#aac42a", "#80bd01", "#33a643"];
var wordColor = [];
var colorIdx = 0;
var matchRegExp = "";
var openLeft = false;
var openRight = false;
// characters to strip from start and end of the input string
var endRegExp = new RegExp('^[^\w]+|[^\w]+$', "g");
// characters used to break up the input string into words
var breakRegExp = new RegExp('[^\w\'-]+', "g");
this.setEndRegExp = function(regex) {
endRegExp = regex;
return endRegExp;
};
this.setBreakRegExp = function(regex) {
breakRegExp = regex;
return breakRegExp;
};
this.setMatchType = function(type)
{
switch(type)
{
case "left":
this.openLeft = false;
this.openRight = true;
break;
case "right":
this.openLeft = true;
this.openRight = false;
break;
case "open":
this.openLeft = this.openRight = true;
break;
default:
this.openLeft = this.openRight = false;
}
};
this.setRegex = function(input)
{
input = input.replace(endRegExp, "");
input = input.replace(breakRegExp, "|");
input = input.replace(/^\||\|$/g, "");
if(input) {
var re = "(" + input + ")";
if(!this.openLeft) {
re = "\b" + re;
}
if(!this.openRight) {
re = re + "\b";
}
matchRegExp = new RegExp(re, "i");
return matchRegExp;
}
return false;
};
this.getRegex = function()
{
var retval = matchRegExp.toString();
retval = retval.replace(/(^\/(\b)?|\(|\)|(\b)?\/i$)/g, "");
retval = retval.replace(/\|/g, " ");
return retval;
};
// recursively apply word highlighting
this.hiliteWords = function(node)
{
if(node === undefined || !node) return;
if(!matchRegExp) return;
if(skipTags.test(node.nodeName)) return;
if(node.hasChildNodes()) {
for(var i=0; i < node.childNodes.length; i++)
this.hiliteWords(node.childNodes[i]);
}
if(node.nodeType == 3) { // NODE_TEXT
if((nv = node.nodeValue) && (regs = matchRegExp.exec(nv))) {
if(!wordColor[regs[0].toLowerCase()]) {
wordColor[regs[0].toLowerCase()] = colors[colorIdx++ % colors.length];
}
var match = document.createElement(hiliteTag);
match.appendChild(document.createTextNode(regs[0]));
match.style.backgroundColor = wordColor[regs[0].toLowerCase()];
match.style.color = "#000";
var after = node.splitText(regs.index);
after.nodeValue = after.nodeValue.substring(regs[0].length);
node.parentNode.insertBefore(match, after);
}
};
};
// remove highlighting
this.remove = function()
{
var arr = document.getElementsByTagName(hiliteTag);
while(arr.length && (el = arr[0])) {
var parent = el.parentNode;
parent.replaceChild(el.firstChild, el);
parent.normalize();
}
};
// start highlighting at target node
this.apply = function(input)
{
this.remove();
if(input === undefined || !(input = input.replace(/(^\s+|\s+$)/g, ""))) {
return;
}
if(this.setRegex(input)) {
this.hiliteWords(targetNode);
}
return matchRegExp;
};
}
<!-- Search field -->
<input type="text" id="keywords" placeholder="Search on the page..."></input>
<div id="txt"><div class="faq-question"><h4>What is Lorem Ipsum?</h4>
<p>Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book. It has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged. It was popularised in the 1960s with the release of Letraset sheets containing Lorem Ipsum passages, and more recently with desktop publishing software like Aldus PageMaker including versions of Lorem Ipsum.</p></div>
<div class="faq-question"><h4>Why do we use it?</h4>
<p>It is a long established fact that a reader will be distracted by the readable content of a page when looking at its layout. The point of using Lorem Ipsum is that it has a more-or-less normal distribution of letters, as opposed to using 'Content here, content here', making it look like readable English. Many desktop publishing packages and web page editors now use Lorem Ipsum as their default model text, and a search for 'lorem ipsum' will uncover many web sites still in their infancy. Various versions have evolved over the years, sometimes by accident, sometimes on purpose (injected humour and the like).</p></div>
<div class="faq-question"><h4>Where does it come from?</h4>
<p>Contrary to popular belief, Lorem Ipsum is not simply random text. It has roots in a piece of classical Latin literature from 45 BC, making it over 2000 years old. Richard McClintock, a Latin professor at Hampden-Sydney College in Virginia, looked up one of the more obscure Latin words, consectetur, from a Lorem Ipsum passage, and going through the cites of the word in classical literature, discovered the undoubtable source. Lorem Ipsum comes from sections 1.10.32 and 1.10.33 of "de Finibus Bonorum et Malorum" (The Extremes of Good and Evil) by Cicero, written in 45 BC. This book is a treatise on the theory of ethics, very popular during the Renaissance. The first line of Lorem Ipsum, "Lorem ipsum dolor sit amet..", comes from a line in section 1.10.32.</p></div></div>
<style>
.sticky-faqsearch {position: sticky; top: 30px; box-shadow: 0px 5px 10px #4f4f5d29;}
</style>
<script type="text/javascript">
//highlight searched keyword
window.addEventListener("DOMContentLoaded", function(e) {
var myHilitor2 = new Hilitor("playground");
myHilitor2.setMatchType("left");
document.getElementById("keywords").addEventListener("keyup", function(e) {
myHilitor2.apply(this.value);
//Hide unrelated search results (hides faq-question with no matches to input)
var questions = document.getElementsByClassName("faq-question");
for(x = 0; x < questions.length; x++) {
if(questions[x].getElementsByTagName('mark').length){
questions[x].style.display = "block";
// console.log("input exists");
} else {
questions[x].style.display = "none";
// console.log("no matched keywords in this section");
}
//if page doesnt contain mark set display to block
if (document.getElementsByTagName('mark').length == 0) {
questions[x].style.display = "block";
// console.log("no input");
}
}
//scroll to searched keyword
var element = document.getElementsByTagName("mark")[0];
if(element){
window.scroll({top: element.offsetTop, behavior: 'smooth'});
}
////////////////////////////////////////////////////////////////////////
//scroll to searched keyword
if (e.key === 'Enter') {
var elements = document.getElementsByTagName("mark");
if (count < elements.length) {
window.scroll({top: elements[++count].offsetTop, behavior: 'smooth'})
} else {
count = 0;
window.scroll({top: elements[0].offsetTop, behavior: 'smooth'});
}
console.log("length " + elements.length);
} else {
count = 0;
var element = document.getElementsByTagName("mark")[0];
if(element){
window.scroll({top: element.offsetTop, behavior: 'smooth'});
}
}
console.log(count);
/////////////////////////////////////////////////////////////////////////
}, false);
}, false);
//search bar sticks to the top on scroll
window.onscroll = function() {seatchStickToTop()};
var faqsearch = document.getElementById("keywords");
var sticky = faqsearch.offsetTop;
function seatchStickToTop() {
if (window.pageYOffset > sticky) {
faqsearch.classList.add("sticky-faqsearch");
} else {
faqsearch.classList.remove("sticky-faqsearch");
}
}
</script>
让我们检查一下您的这部分代码：
if (count < elements.length) {
window.scroll({top: elements[++count].offsetTop, behavior: 'smooth'})
} else {
count = 0;
window.scroll({top: elements[0].offsetTop, behavior: 'smooth'});
}
count < elements.length时，你经过第一个分支。在那里，您使用 ++count，这意味着如果 count 最初是 elements.length - 1，您现在正试图访问超出范围的 elements[elements.length]，因此 undefined.
只需检查 if (count + 1 < elements.length) 就可以了，即“下一个元素还在列表中吗？”基本上。