CODEWITHSUNDEEP
javascriptfor-loop
soum
soum

Reputation: 1159

pushing objects in a array inside a loop

I am trying to push objects into an array inside a for loop. The expected data structure is 

[{"valueItem":"item0"}, {"valueItem":"item1"}, {"valueItem":"item2"}, {"valueItem":"item3"}, {"valueItem":"item4"}]

The code I have is 

var arr = [];
var obj = {};

for(var i = 0; i < 5; i++){
  arr.push(obj.valueItem = 'item'+i);
}

console.log(arr)

But the what I get back is 

["item0", "item1", "item2", "item3", "item4"]

What am I doing wrong?

Upvotes: 0

Views: 3865

Answers (6)

user949300
user949300

Reputation: 15729

Your expected result has a different object for each element. Even though they are are similar in that they have a valueItem proprerty, they are all different. So you need to create a new one on each loop iteration. You need

arr.push({valueItem:"item"+i});

which creates a new one each time.

Upvotes: 0

Mohammad Hamedani
Mohammad Hamedani

Reputation: 3354

First define object, then push it to array:

var arr = [];

for(var i = 0; i < 5; i++){
  arr.push({valueItem: 'item'+i});
}

console.log(arr)

Based on your try:

var arr = [];

for(var i = 0; i < 5; i++){
  var obj = {};
  obj.valueItem = 'item'+i
  arr.push(obj);
}

console.log(arr)

Upvotes: 1

JackKalish
JackKalish

Reputation: 1585

The below works ;)

var arr = [];

for(var i = 0; i < 5; i++){
  var obj = {};
  obj.valueItem = 'item' + i;
  arr.push(obj);
}

console.log(arr)

Upvotes: 1

R_Ice
R_Ice

Reputation: 684

try:arr.push({"valueItem":"item"+i});

Ok, to clarify, you have to push an object in your array to get your expected array. push(obj.valueItem = 'item'+i) works sortof because you are assigning inside push.

Upvotes: 2

Faris
Faris

Reputation: 544

By doing this arr.push(obj.valueItem = 'item'+i);

you are not pushing obj into the array, you are making an assignment

obj.valueItem = 'item'+i

the result of an assignment is the returned value, in this case it is item+i,

to push objects into an array do this 

arr.push({
  valueItem: "item0"
})

Upvotes: 1

Fiid
Fiid

Reputation: 1840

Looks like you're not actually creating a new object for each loop. Maybe try:

arr.push( { valueItem: 'item'+i } );.

The {} will create a new hash object, which we would push onto the array.

In your inital code you only made one object, so the thing you were pushing was the return value of obj.valueItem='item'+i. Since the return value of a string assignment would be the actual string, you were just creating an array of strings.

Upvotes: 0

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