Question

我正在阅读一篇声明_.parseInt安全的博客。根据文档，它也接受基数作为本机parseInt的第二个参数。通常在映射数组时，直接将parseInt传递给map时会遇到意外行为。

lodash的parseInt如何安全地工作？

var a = ['2', '3', '4', '5', '6', '7', '8']

//case 1:    
_.map(a, parseInt)
//[2, NaN, NaN, NaN, NaN, NaN, NaN] -  this is the expected output

//case 2:    
_.map(a, (num, index) => _.parseInt(num, index))
//[2, NaN, NaN, NaN, NaN, NaN, NaN] -  this is the expected output

//case 3:    
_.map(a, _.parseInt)
//[2, 3, 4, 5, 6, 7, 8] -  how is this working correctly?

案例2与案例3有什么不同？

Answer 1

_.parseInt的{{3}}采用“秘密”第三个参数。

如果提供了第三个参数，就像在_.map(a, _.parseInt)回调中一样，则忽略第二个参数。

var a = ['2', '3', '4', '5', '6', '7', '8'];

// With two arguments:
console.log(_.map(a, (num, index) => _.parseInt(num, index)));
//[2, NaN, NaN, NaN, NaN, NaN, NaN] -  this is the expected output

// With all three arguments that _.map provides:
console.log(_.map(a, (num, index, arr) => _.parseInt(num, index, arr)));
//[2, 3, 4, 5, 6, 7, 8]

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.4/lodash.min.js"></script>

lodash的_.parseInt如何在地图上安全地解析

1 个答案: