isFinite方法详解
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MDN中描述isFinite()函数:确定函数的参数是否为有限数,可以将参数转化为数字,
JS高程设计这样描述isFinite()函数:在参数位于最小与最大数值之间时会返回true
综上:isFinite()方法就是在-Infinity和Infinity之间返回true,否则返回false;
Number.MAX_VALUE + 1 === Number.MAX_VALUE + 2 //trueNumber.MAX_VALUE + 1 === Number.MAX_VALUE + 999999 //trueNumber.MAX_VALUE + 1 === Number.MAX_VALUE + 999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999 // true运用科学计数法可以这样写:Number.MAX_VALUE + 1 === Number.MAX_VALUE + (1e+291)当在增加一个9时,就会变成falseNumber.MAX_VALUE + 1 === Number.MAX_VALUE + 9999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999 // false科学计数法也可以这样写:Number.MAX_VALUE + 1 === Number.MAX_VALUE + (1e+292)
但是对于乘法却是比较诡异:Number.MAX_VALUE * 1.00000001 === Infinity
所以:isFinite(Number.MAX_VALUE * 1.00000001) //falseisFinite(Number.MAX_VALUE+(Number.MAX_VALUE)) //false
isFinite(Infinity); // falseisFinite(NaN); // falseisFinite(-Infinity); // falseisFinite(0); // trueisFinite(2e64); // trueisFinite(910); // trueisFinite(null); // trueisFinite('0'); // trueisFinite('hello') //falseisFinite(true) //trueisFinite(false) //true
难点就是判断数据是否为正无穷或者负无穷,规则上面已经提到过!
可以参照如下链接:https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/isFinite
https://stackoverflow.com/questions/10837670/adding-to-number-max-value
https://stackoverflow.com/questions/25532240/isfinitenumber-max-value-1-returns-true
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