JavaScript arrays declaration ways difference

Question

This could be a pretty basic question, in JavaScript, what's difference between:

var userDetails = {};  
var usersList = [];

I was reading an article which had following code:

 function GetSampleUsersList() {  
    var userDetails = {};  
    var usersList = [];  
    for (var i = 1; i <= 3; i++) {  
        userDetails["UserId"] = i;  
        userDetails["UserName"] = "User- " + i;  
        userDetails["Company"] = "Company- " + i;  
        usersList.push(userDetails);  
    }  
    return JSON.stringify(usersList);  
}

Thanks

userDetails = {} is not an array and userDetails["UserId"] is just a bracket notation of accessing object's property — RomanPerekhrest
– RomanPerekhrest, Commented Sep 1, 2016 at 7:20

Wiktor Zychla · Accepted Answer · 2016-09-01 07:22:13Z

2

This is a pretty basic question.

var o = {}

initializes an empty object. Then you assign its properties.

 var a = []

initializes an empty array. You then add the newly created object to the array

a.push( o );

answered Sep 1, 2016 at 7:22

Wiktor Zychla

48.4k6 gold badges82 silver badges114 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Nina Scholz · Accepted Answer · 2016-09-01 07:30:45Z

You are using for every iteration the same userDetails, because you overwrite just the properties and while you have pushed the same object, you have always the same content for every element in the array.

 function GetSampleUsersList() {  
    var userDetails = {};
    var usersList = [];
    for (var i = 1; i <= 3; i++) {
        userDetails["UserId"] = i;
        userDetails["UserName"] = "User- " + i;
        userDetails["Company"] = "Company- " + i;
        usersList.push(userDetails);
    }
    return JSON.stringify(usersList);
}

console.log(GetSampleUsersList());

Better use a new empty object for every loop.

 function GetSampleUsersList() {  
    var userDetails;
    var usersList = [];
    for (var i = 1; i <= 3; i++) {
        userDetails = {}; // this is necessary
        userDetails["UserId"] = i;
        userDetails["UserName"] = "User- " + i;
        userDetails["Company"] = "Company- " + i;
        usersList.push(userDetails);
    }
    return JSON.stringify(usersList);
}
console.log(GetSampleUsersList());

Rahul Pandey · Accepted Answer · 2016-09-01 07:40:35Z

0

function GetSampleUsersList() {      
var userDetails = {};  //created an empty object userDetails 
var usersList = [];  //created an empty array userDetails
for (var i = 1; i <= 3; i++) {  //looping to add property and value in object and for each iteration object is getting pushed into array at an index i.
    userDetails["UserId"] = i;  
    userDetails["UserName"] = "User- " + i;  
    userDetails["Company"] = "Company- " + i;  
    usersList.push(userDetails);  // pushing object {"UserId":i, "UserName":"User-i", "Company":"Company-i"} into array
}  
    return JSON.stringify(usersList);  // Parsing the object into javascript string
}

answered Sep 1, 2016 at 7:40

Rahul Pandey

4551 gold badge4 silver badges13 bronze badges

Comments

Harish Nayak · Accepted Answer · 2016-09-01 08:33:30Z

0

 var userDetails = {}; -- object notation in javascript
 var usersList = [];  is an array notation in javascript.

for more infomation refer here http://yuiblog.com/blog/2006/11/13/javascript-we-hardly-new-ya/

edited Sep 1, 2016 at 8:33

answered Sep 1, 2016 at 7:23

Harish Nayak

3483 silver badges19 bronze badges

1 Comment

abarisone Over a year ago

Please edit with more information. Code-only and "try this" answers are discouraged, because they contain no searchable content, and don't explain why someone should "try this".

Collectives™ on Stack Overflow

JavaScript arrays declaration ways difference

4 Answers 4

Comments

Comments

Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

Comments

Comments

Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related