Get length of every element in array - JavaScript

Question

I want to get length of every element in array

my code is

var a = "Hello world" ; 
var chars = a.split(' '); 

so I will have an array of

chars = ['Hello' , 'world'] ; 

but how I can get length of each word like this ?

Hello = 5 
world = 5

Answer 1

You can use map Array function:

var lengths = chars.map(function(word){
 return word.length
}) 

Answer 2

ES6 is now widely available (2019年10月03日) so for completeness — you can use the arrow operator with .map()

var words = [ "Hello", "World", "I", "am", "here" ];
words.map(w => w.length);
> Array [ 5, 5, 1, 2, 4 ]

or, very succinctly

"Hello World I am here".split(' ').map(w => w.length)
> Array [ 5, 5, 1, 2, 4 ]

• friedi: Or you can do it with array comprehension: [for (word of words) word.length]
• Stephen P: @friedi - nice also! but MDN warns "Non-standard. Do not use!" ... this was removed from the ES6 draft; it could conceivably end up in ES7, and MDN compatibility chart shows only Firefox currently supports it. Still cool.
• Cristofayre: I'm lost! OK, so "words" is an array, and "words.map" gets the length of each word, which it stored in an array as "> Array[5,5,1,2,4]. But how to access the cells of that latter array? What is it's name?
• Stephen P: @Cristofayre - in my answer the examples are from typing in the browser console, and I'm not assigning the result of words.map to anything. You would want to do something like let wordLengths = words.map(w => w.length); then you an access the latter array as wordLengths[i] just like any other array. In the browser console I use var but in actual js code I never use it; I use const and let.

Answer 3

The key here is to use .length property of a string:

 for (var i=0;i<chars.length;i++){
 console.log(chars[i].length);
 }

Answer 4

You could create a results object (so you have the key, "hello", and the length, 5):

function getLengthOfWords(str) {
 var results = {}; 
 var chars = str.split(' ');
 chars.forEach(function(item) {
 results[item] = item.length;
 });
 return results;
}
getLengthOfWords("Hello world"); // {'hello': 5, 'world': 5}

Answer 5

Try map()

var words = ['Hello', 'world'];
var lengths = words.map(function(word) {
 return word + ' = ' + word.length;
});
console.log(lengths);

Answer 6

You can use forEach, if you want to keep the words, and the length you can do it like this:

var a = "Hello world" ; 
var chars = a.split(' ');
 var words = [];
 chars.forEach(function(str) { 
 words.push([str, str.length]);
 });

You can then access both the size and the word in the array.

Optionally you could have a little POJO object, for easier access:

var a = "Hello world" ; 
var chars = a.split(' ');
var words = [];
chars.forEach(function(str) { 
 words.push({word: str, length: str.length});
});

Then you can access them like:

console.log(words[0].length); //5
console.log(words[0].word); //"Hello"

Or using map to get the same POJO:

var words = chars.map(function(str) { 
 return {word: str, length: str.length};
});