Array.push() doesn't work as expected [duplicate]

Question

I have an array. For test purposes i output its contents like this:

for (var i=0; i<array1.length; i++){
        console.log(i + ':' + array1[i]);
    }


0:String1
1:String2

Now i have a second array. What i want to do is push the contents of array1, into array2.

I do this with this line:

array2.push(array1);

Unfortunately, the contents aof the first array, exist in only one index of the second array. Separated by commas.

For example, if we use view the contents of the second array after the action it will be something like this:

for (var i=0; i<array1.length; i++){
        console.log(i + ':' + array1[i]);
    }


0:Old_string1
1:Old_string2
2:Old_string3
3:Old_string4
4:String1,String2

While i would like this outout:

4:String1
5:String2

Answer 1

You should try with:

array2 = array2.concat(array1);

or with ES6 destructuring

array2.push(...array1);

Answer 2

Array.push doesn't do that. You need Array.concat :

var array1 = ['a', 'b', 'c'];
var array2 = ['d', 'e', 'f'];

console.log(array1.concat(array2));
// expected output: Array ["a", "b", "c", "d", "e", "f"]

Answer 3

array.push will push one or more objects to the array. You can not pass a full array in the push() method, or the contents will be counted as one object. To combine the two arrays into one, use concat.

Answer 4

You should use the spread operator (...) to destruct the values held in array1 and push those into array2. Like so:

array2.push(...array1);

This will separate all the strings held in array1 into individual values and then push them in. A nice little bit of syntactic sugar introduced in ES6.

Answer 5

Use push and apply:

const a1 = ["all", "my", "strings"];
const a2 = ["belong", "together"];
Array.prototype.push.apply(a1, a2);
console.log(a1);