CODEWITHSUNDEEP
javascript
Chris Clark
Chris Clark

Reputation: 397

Why this .map Function Does Not Work

There is this quite simple .map function

var numbers = [1, 4, 9];
var roots = numbers.map(Math.sqrt);

This makes sense, I perform on numbers the map function and provide a function that will iterate through on each element in the array.

In this next example (all these taken from mozilla, https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/map) , I thought to myself why would we use Array.prototype.map.call, maybe they are just demonstrating different ways to accomplish the same goal.

var str = '12345';
Array.prototype.map.call(str, function(x) {
  return x;
}).reverse().join('');

So I rewrote this as

var str = '12345';
var stringy = str.map(function(x) {
  return x;
}).reverse().join('');

Except I get an error "str.map is not a function(...)" Why is this?

Upvotes: 0

Views: 395

Answers (1)

Maurizio Ferreira
Maurizio Ferreira

Reputation: 476

This is because str is a string, and strings do not have the map() function.

map() is a function of the array type.

Upvotes: 4

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