Error in following code:-
var x = [{id: 'abc'}, {id: 'xyz'}];
var index = x.indexOf({id: 'abc'});
What's the syntax for above?
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1That's not a syntax problem. Two objects with different references in memory are different in JS.Denys Séguret– Denys Séguret2013-11-14 14:16:42 +00:00Commented Nov 14, 2013 at 14:16
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6 Answers
You should pass reference to exactly the same object you have defined in the array:
var a = {id: 'abc'},
b = {id: 'xyz'};
var index = [a, b].indexOf(a); // 0
2 Comments
Sangram Singh
It didn't work when i tried it though.
JVM
This is working for me..!!
Objects are only equal to each other if they refer to the exact same instance of the object.
You would need to implement your own search feature. For example:
Array.prototype.indexOfObject = function(obj) {
var l = this.length, i, k, ok;
for( i=0; i<l; i++) {
ok = true;
for( k in obj) if( obj.hasOwnProperty(k)) {
if( this[i][k] !== obj[k]) {
ok = false;
break;
}
}
if( ok) return i;
}
return -1; // no match
};
var x = [{id: 'abc'}, {id: 'xyz'}];
var index = x.indexOfObject({id: 'abc'}); // 0
answered Nov 14, 2013 at 14:26
Niet the Dark Absol
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3 Comments
VisioN
this[i].k --> this[i][k].
Niet the Dark Absol
@VisioN You saw nothing! :p
VisioN
@Kolink Yeah, yeah, yeah...
;)Iterate through the array like this:
for(var i = 0, len = x.length; i < len; i++) {
if (x[i].id === 'abc') {
console.log(i);
break;
}
}
Otherwise, you'll have to make sure the pointers are the same for the objects you're trying to look for with indexOf
Comments
Let's have some nice code here ;)
Underscore.js provides where, which is also fairly easy to write in pure JS:
Array.prototype.where = function(props) {
return this.filter(function(e) {
for (var p in props)
if (e[p] !== props[p])
return false;
return true;
});
}
Another (more flexible) function understands either an object or a function as a selector:
Array.prototype.indexBy = function(selector) {
var fn = typeof selector == "function" ? selector :
function(elem) {
return Object.keys(selector).every(function(k) {
return elem[k] === selector[k]
})
}
return this.map(fn).indexOf(true);
}
and then
var x = [{id: 'abc'}, {id: 'xyz'}];
x.indexBy({'id': 'xyz'}) // works
x.indexBy(function(elem) { return elem.id == 'xyz' }) // works too
Comments
var o = {}
var x = [o]
console.log(x.indexOf(o))
With x.indexOf({}) you create a new Object the is not present in the array
Comments
The following is the most wonderful method:-
var indexId = x.map(function(e) { return e.id; }).indexOf('abc');
as seen in this answer
