文本输入总是被 jQuery 解析为字符串 - 如何将 val 检索为 int 或 float？

Question

我正在根据两个文本输入的值进行一些计算。值可以是浮点数或整数。计算在 keyup 事件上触发。

所以目前我必须评估 val 以确定它是 float 还是 int，然后根据需要使用 parseInt 或 parseFloat。

这似乎有点老套或矫枉过正。有更好的方法吗？

这里有一个fiddle来演示：https://jsfiddle.net/2hw0tnhb/

HTML:

<label id="x-label" for="x">Float</label>
<br/>
<input type="text" name="x" id="x" value="29.7" class="axis"/>

<br/>
<br/>

<label id="y-label" for="y">Int</label>
<br/>
<input type="text" name="y" id="y" value="21" class="axis"/>

JS:

var $x = $('#x');
var $y = $('#y');
var $axis = $('.axis');
var x_label = $('#x-label');
var y_label = $('#y-label');

$axis.keyup(function(){

    var $this = $(this);
    var val = $this.val();
    var axis = 'x';

    if($this.attr('id') === 'y') axis = 'y';

    //check if int or float:
    if(parseFloat(val) > Math.floor(parseFloat(val))){
        //it is a float - use parseFloat()   
        if( axis === 'x' ){
           x_label.text('Float'); 
        }else{
           y_label.text('Float'); 
        }        
    }
    else{
        //it is an int - use parseInt()
        if( axis === 'x' ){
           x_label.text('Int'); 
        }else{
           y_label.text('Int'); 
        }
    }
});

Answer 1

您可以使用前导 +，结果将为数字、整数或浮点数：

var val = +$this.val(); //or +this.value

并且您可以使用 type="number" 将条目保存到 .axis 数字中：

<input type="number" name="x" id="x" value="29.7" class="axis"/>

$(function() {
    var $x = $('#x');
    var $y = $('#y');
    var $axis = $('.axis');
    var x_label = $('#x-label');
    var y_label = $('#y-label');

    $axis.keyup(function(){

        var $this = $(this);
        var val = +$this.val();
        var axis = this.name;
        
        console.log( val );
        console.log( val + 3.5 );
        console.log( val + 4 );
    })
    .trigger('keyup');
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<label id="x-label" for="x">Float</label>
<br/>
<input type="number" name="x" id="x" value="29.7" class="axis"/>

<br/>
<br/>

<label id="y-label" for="y">Int</label>
<br/>
<input type="number" name="y" id="y" value="21" class="axis"/>

Unary plus (+)
The unary plus operator precedes its operand and evaluates to its operand but attempts to converts it into a number, if it isn't already. Although unary negation (-) also can convert non-numbers, unary plus is the fastest and preferred way of converting something into a number, because it does not perform any other operations on the number. It can convert string representations of integers and floats, as well as the non-string values true, false, and null. Integers in both decimal and hexadecimal ("0x"-prefixed) formats are supported. Negative numbers are supported (though not for hex). If it cannot parse a particular value, it will evaluate to NaN.

参考：Arithmetic Operators

Answer 2

这看起来很老套，是的，但这是 JavaScript 类型系统的不幸副作用之一。可以通过 looking for a remainder when dividing by 1:

检查数字是否为整数

function isInt(n) {
    return n % 1 === 0;
}

您也可以稍微重构一下代码，让它看起来不那么臃肿：

$axis.keyup(function(){
    var $this = $(this);
    var axis = $this.attr('id');
    var val = $this.val();
    var isInt = isInt(val);
    var text = (isInt) ? 'Int' : 'Float';

    var labelMap = {
        x: x_label,
        y: y_label
    };

    labelMap[axis].text(text);
});

文本输入总是被 jQuery 解析为字符串 - 如何将 val 检索为 int 或 float？

Text input always parsed as string by jQuery - how to retrieve val as int or float?

html

javascript

jquery

user-input