How to overwrite an element in javascript object array

Question

I want to do the following in javascript but there's something about the syntax I'm not understanding here:

var theObj = { foo: val1, bar: val2 }
if ( condition ) {
  theObj[foo] = newVal
  return theObj // returns { foo: val1, bar: newVal } 
}
return theObj // returns { foo: val1, bar: val2 }

I know there was a syntax error there, whoops, got it now!

Brian
– Brian

2012-08-15 15:46:08 +00:00
Commented Aug 15, 2012 at 15:46 — Brian
– Brian, Commented Aug 15, 2012 at 15:46

Michael Berkowski · Accepted Answer · 2012-08-15 15:51:58Z

3

What you have is not an object array, but rather an object literal. Normally, its properties would be accessed as theObj.property, but JavaScript provides an alternative syntax of theObj["property"] when you need to do operations like string manipulation on the property name (like theObj["property_" + numberVar]), or for properties not valid in dot notation (like number properties theObj[12] = "twelve")

If you access the property via [], you would need to quote the string ["foo"], otherwise the parser would be looking for a variable named foo to insert there. However, this simple string property is better accessed with dot notation:

if ( condition ) {
  theObj.foo = newVal
  return theObj // returns { foo: val1, bar: newVal } 
}

edited Aug 15, 2012 at 15:51

answered Aug 15, 2012 at 15:46

Michael Berkowski

271k47 gold badges450 silver badges395 bronze badges

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

1 Comment

Esailija Over a year ago

Bracket access is also needed when what would otherwise be invalid dot access syntax: var obj = {1e5: 3}; alert(obj[1e5])

Collectives™ on Stack Overflow

How to overwrite an element in javascript object array

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related