js比较数字相等

示例代码：
<!DOCTYPE html>

<html lang="zh">

    <head>

        <meta charset="UTF-8" />

        <title>js比较数字相等</title>

    </head>

    <body>

        <script type="text/javascript">

            //设置误差范围值--机器精度（对于js来说是2^-52）

            //ES6定义了Number.EPSILON，之前未定义Number.EPSILON

            if(!Number.EPSILON) {

                Number.EPSILON = Math.pow(2, -52)

            }

            function numberCloseEnoughToEqual(a, b) {

                return(a - b) < Number.EPSILON;

            }

            console.log(numberCloseEnoughToEqual((0.1 + 0.2), 0.3)); //true

        </script>

    </body>

</html>