why the value of a[0].nil is 400. what should i do to set it to 200. thanks for the answer
a = new Array();
x = new Object();
str = "nil";
x[str] = 200;
a.push(x);
x[str] = 400;
a.push(x);
alert("1 = "+ a[0].nil);
alert("2 = "+ a[1].nil);
Add a comment
|
3 Answers
Because you are pushing reference of object x to array a, not copy of that object.
After modifying value of x[str], a[0] reference pointing to updated object.
So in your code a[0],a[1] and xpointing to same object. If you wish to add copy of x object in particular moment of code execution you have to clone your object x and push clone into array.
SO question How do I correctly clone a JavaScript object? will help you in cloning js object. Also see article "JavaScript: Passing by Value or by Reference" to get better idea of variable passing in javascript.
Good Luck!
Comments
why the value of a[0].nil is 400
Because x still points to old reference which you haven't changed (you only changed value of property inside it).
what should i do to set it to 200
Simply before
x[str] = 400;
add this line
x = {}; //x = new Object();
1 Comment
gurvinder372
@AhmadBudiU Glad to help. Accept and upvote the answer that has helped you. meta.stackexchange.com/questions/5234/…
You should clone object, with Object.assing as
The Object.assign() method is used to copy the values of all enumerable own properties from one or more source objects to a target object. It will return the target object.
a = new Array();
x = new Object();
str = "nil";
x[str] = 200;
a.push(Object.assign({}, x));
x[str] = 400;
a.push(Object.assign({}, x));
document.write("1 = "+ a[0].nil);
document.write("2 = "+ a[1].nil);
answered May 17, 2016 at 10:15
Krzysztof Safjanowski
7,4483 gold badges38 silver badges50 bronze badges
Comments
