为什么我的 javascript return 不是我想要的值?
Why won't my javascript return the values i want?
我正在尝试使用一个函数在 canvas 上绘制一个矩形。第一步是找到鼠标点击的点。这是我正在使用的代码:
wbtCanvas = document.getElementById("wbtCanvas");
function relMouseCoords(event){
var totalOffsetX = 0; //coordinates of corner of canvas
var totalOffsetY = 0;
var canvasX = 0;
var canvasY = 0;
var wbtCanvas = this; //what called the event
do{
totalOffsetX += wbtCanvas.offsetLeft - wbtCanvas.scrollLeft; //relative coordinates
totalOffsetY += wbtCanvas.offsetTop - wbtCanvas.scrollTop;
}
while(wbtCanvas = wbtCanvas.offsetParent)
canvasX = event.pageX - totalOffsetX;
canvasY = event.pageY - totalOffsetY;
point = {x:canvasX, y:canvasY};
console.log("{" + point.x + ", " + point.y + "}");
return point; //object returned
}
function drawRectangle(){
x = relMouseCoords.x;
y = relMouseCoords.y;
console.log(x + " " + y);
}
当我在控制台中调用函数 drawRectangle() 时,确保我的鼠标指针位于 canvas 上,它会给出以下响应:
"undefined undefined"
relMouseCoords
是一个函数,您必须调用它并使用 return 值:
function drawRectangle() {
var coords = relMouseCoords();
console.log (coords.x + " " + coords.y);
}
一方面,您需要调用 relMouseCoords
函数。
我正在尝试使用一个函数在 canvas 上绘制一个矩形。第一步是找到鼠标点击的点。这是我正在使用的代码:
wbtCanvas = document.getElementById("wbtCanvas");
function relMouseCoords(event){
var totalOffsetX = 0; //coordinates of corner of canvas
var totalOffsetY = 0;
var canvasX = 0;
var canvasY = 0;
var wbtCanvas = this; //what called the event
do{
totalOffsetX += wbtCanvas.offsetLeft - wbtCanvas.scrollLeft; //relative coordinates
totalOffsetY += wbtCanvas.offsetTop - wbtCanvas.scrollTop;
}
while(wbtCanvas = wbtCanvas.offsetParent)
canvasX = event.pageX - totalOffsetX;
canvasY = event.pageY - totalOffsetY;
point = {x:canvasX, y:canvasY};
console.log("{" + point.x + ", " + point.y + "}");
return point; //object returned
}
function drawRectangle(){
x = relMouseCoords.x;
y = relMouseCoords.y;
console.log(x + " " + y);
}
当我在控制台中调用函数 drawRectangle() 时,确保我的鼠标指针位于 canvas 上,它会给出以下响应:
"undefined undefined"
relMouseCoords
是一个函数,您必须调用它并使用 return 值:
function drawRectangle() {
var coords = relMouseCoords();
console.log (coords.x + " " + coords.y);
}
一方面,您需要调用 relMouseCoords
函数。