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javascript - It is possible to use eval to test an equality?

问题描述:

I try to get a boolean return from a simple condition. it is possible to use Eval function to do that or may I have to use a if statement ?

here is my expression :

alert(eval($("#val1").val() + $("#val2").val() == $("#result1").val()));

It's numeric values like 1 + 1 = 2 // true

网友答案:

You should convert them to numbers like this:

alert(Number($("#val1").val()) + Number($("#val2").val()) ==  Number($("#result1").val()));

if you don't convert them to numbers,java-script assumes they are strings and does a concatenation, and then val1(1) + val2(1) = 11

$("#btn").click(function(){
     console.log("Converted To Numbers: " + $("#val1").val() + " + " + $("#val2").val() + " = " + (Number($("#val1").val()) + Number($("#val2").val())));
    alert(Number($("#val1").val()) + Number($("#val2").val()) ==  Number($("#result1").val()) );
});

$("#btn2").click(function(){
    console.log("No Conversion: " + $("#val1").val() + " + " + $("#val2").val() + " = " + $("#val1").val() + $("#val2").val());
    alert($("#val1").val() + $("#val2").val() == $("#result1").val() );
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<input type="text" id="val1">
<input type="text" id="val2">
<input type="text" id="result1">
<br>
<input type="button" id="btn" value="Convert To Numbers">
<input type="button" id="btn2" value="No Conversion">
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