In Javascript how do I detect different kinds of elements in an array containing sub arrays and single elements?

Question

I am being given data in an array that contains sub arrays and single elements. I do not know how many elements in the main array are sub arrays, or how many are single elements, or how many elements will be in a sub array, or where the sub arrays will be in the main array.

Is there a way I can detect the sub arrays or the single elements?

Example:

array[ [1,2,3], 4, 5]

Bartek: OK - Can you please give me a code example of how I could detect the sub array using that other question with answers? — Junco, Dec 17 '15 at 16:18
I tried that. But, when I use array[0] I get 1. I thought I would get that sub array. But, I only get 1. Don't I have to use array[0][0] to get 1 ? — Junco, Dec 17 '15 at 16:20

Adrian Lynch · Accepted Answer · 2015-12-17T19:54:08.317

4

Loop and check:

[1,2,[4,5],3].forEach((item, i) => {
    if (Array.isArray(item)) {
        console.log(`Item ${i} is an array!`); // Item 2 is an array!
    }
})

Or map to booleans:

[1,2,[4,5],3].map(Array.isArray); // [false, false, true, false]

edited Dec 17 '15 at 19:54

answered Dec 17 '15 at 16:21

Adrian Lynch

8,237
2
32
40

provided you don't need to support legacy javascript engines (really old browsers), this is the correct answer. If you _do_ need to support legacy browsers, add this polyfill: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/isArray – code_monk Dec 17 '15 at 16:27

score 0 · Answer 2 · edited May 23 '17 at 12:33

You can use the operator typeof.

typeof 1; //number
typeof 'hola'; //string

Although you keep warning in that typeof array is object. So you need check the class using instanceof method (or the static method Array.isArray(your_variable)). For this issue you can read this question (How do you check if a variable is an array in JavaScript?).

In your particular case

[1, 2, 3, ['a','b']].forEach(function(element){
    if(typeof(element) === 'number'){
       //todo
    }elseif(typeof(element) === 'string'){
      //todo
    }elseif(Array.isArray(element){
        //todo array element
    }
});

score 0 · Answer 3 · answered Dec 17 '15 at 16:24

0

Using instanceof:

 for(var i=0;i<your_array.length;i++){
        if(your_array[i] instanceof Array){
               console.log("Subarray!");
        }else{
               console.log("Not Subarray!");
        }
 }

answered Dec 17 '15 at 16:24

Calancea Bogdan

79
7

In Javascript how do I detect different kinds of elements in an array containing sub arrays and single elements?

3 Answers3