Javascript - Compare without typecasting to boolean
In other languages I have two sets of operators, or
and ||
, which typecast differently. Does Javascript have a s开发者_高级运维et of operators to compare and return the original object, rather than a boolean value?
I want to be able to return whichever value is defined, with a single statement like var foo = bar.name or bar.title
There is only one set of boolean operators (||
, &&
) and they already do that.
var bar = {
name: "",
title: "foo"
};
var foo = bar.name || bar.title;
alert(foo); // alerts 'title'
Of course you have to keep in mind which values evaluate to false.
var foo = (bar.name != undefined) ? bar.name :
((bar.title != undefined) ? bar.title : 'error');
var foo = bar.name || bar.title;
It returns the first defined object.
If none of both is defined, undefined
is returned.
I either completely missunderstood the question or it's just straighforward like you mentioned:
var foo = bar.name || bar.title;
if bar.name
contains any truthy value it's assigned into foo
, otherwise bar.title
is assigned.
for instance:
var bar = {
name: null,
title: 'Foobar'
};
var foo = bar.name || bar.title
console.log( foo ); // 'Foobar'
Javascript behaves exactly like you want:
var a = [1, 2],
b = [3, 4];
console.log(a || b); //will output [1, 2]
a = 0;
console.log(a || b); //will outout [3, 4]
If you whant to typecast to boolean you can use double negative operator:
console.log(!![1, 2]); //will output true
console.log(!!0); //will output false
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