["1", "2", "3"].map (parseint)?

["1", "2", "3"].map (parseint) Get what?

The answer is: [1, Nan, Nan].

Cause: parseint receives two parameters, and map passes 3 parameters.

The map function defines :

Arr.map (Callback[,thisarg]);

The callback function requires the following 3 values:

CurrentValue: Current processing value
Index: The indexed value of the numeric value processed
function values handled by the ARRAY:MAP function

Thisarg is optional. The this value in the callback function defaults to the Window object

parseint function Definition:

parseint (stringradix);

String: The character that needs to be converted, if not the string will be converted, ignoring whitespace.

Radix: integer type before the number 2-36. By default, 10 is used, which indicates decimal.

It is important to note that radix returns Nan if it is outside 2-36.

Execute the following function:

var function (String, Radix, others) {    return string + '-' + radix + '-' + others;}; [' 1 ', ' 2 ', ' 3 '].map (parseint);

Get:

If you put it in the parseint function:

parseint (' 1 ', 0);p arseint (' 2 ', 1);p arseint (' 3 ', 2);

So get 1,nan,nan

Other uses of the map function:

Example 1: Traversing a Queryselectorall object and executing related functions

var elems = Document.queryselectorall (' div '); var function (elem) {    return  elem;});

Example 2: Reversing a string

var str = ' 12345 'function(x) {    return  x;}). Reverse (). Join ();

Attached: This method can judge Palindrome

var str = ' 12345 '; var function (x) {    return  x;}). Reverse (). Join (); if (str = = = str1) {   console.log ('true 'else  {   console.log (' false ') );}

["1", "2", "3"].map (parseint)?