【笔记】JavaScript编码规范- 类型分配&强制转换

执行强制类型转换语句。

String

// bad <p>// => this.reviewScore = 9;</p>
var A= this.reviewScore + '';


// good
var totalScore = '' + this.reviewScore;


// bad
var totalScore = '' + this.reviewScore + ' total score';


// good
var totalScore = this.reviewScore + ' total score';

使用parseInt对Numbers进行转换，并带一个进制作为参数

var A= '4';

// bad
var val = new Number(A);

// bad
var val = +A;

// bad
var val = A>> 0;

// bad
var val = parseInt(A);

// good
var val = Number(A);


// good
var val = parseInt(A, 10);

无论出于什么原因，或许你做了一些”粗野”的事；或许parseInt成了你的瓶颈；或许考虑到性能，需要使用位运算，都要用注释说明你为什么这么做

// good
/**
* parseInt was the reason my code was slow.
* Bitshifting the String to coerce it to a
* Number made it a lot faster.
*/
var val = inputValue >> 0;

注意：当使用位运算时，Numbers被视为64位值，但是位运算总是返回32位整型(source)。对于整型值大于32位的进行位运算将导致不可预见的行为。Discussion.最大的有符号32位整数是2,147,483,647

2147483647 >> 0 //=> 2147483647
2147483648 >> 0 //=> -2147483648
2147483649 >> 0 //=> -2147483647

Booleans:

var age = 0;

// bad
var hasAge = new Boolean(age);

// good
var hasAge = Boolean(age);

// good
var hasAge = !!age;

1:14 And God said,Let there be lights in the firmament of the heaven to divide the day from the night;and let them be for signs,and for seasons,and for days,and years: