javascript - jQuery 执行数学运算

Question

HTML 用户输入:

=110*200

jQuery:

   $(document).on("change", ".calculator", function(){
        var value = $(this).val();
        if(value.charAt(0) == '='){
            var newval = value.slice(1);
            console.log(parseInt(newval));
        }
    })

输出:

110

谁能告诉我如何使用这个程序进行数学运算？我哪里出错了，为什么它不起作用？

Answer 1

发生这种情况是因为您从未评估表达式本身。您将字符串表达式转换为整数，它从表达式中获取可识别的整数部分，并在 * 字符处将其断开。

Evaluate your expression with eval, and it will get calculated. Alternatively, you can also use Function construct as described in answer here to evaluate this expression.

$(document).on("change", ".calculator", function(){
        var value = $(this).val();
        console.log(value.charAt(0));
        if(value.charAt(0) == '='){
            var newval = value.slice(1);
            console.log(parseInt(eval(newval)));
            console.log(new Function('return ' + newval)());
        }
    })
    
  

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<input class="calculator" type="text">