Comma operator in JS
Apart from being just a delimiter, the comma operator allows you to put multiple statements in a place where one statement is expected. Eg:-
for(var i=0, j=0; i<5; i++, j++, j++){
console.log("i:"+i+", j:"+j);
}
Output:-
i:0, j:0
i:1, j:2
i:2, j:4
i:3, j:6
i:4, j:8
When placed in an expression, it evaluates every expression from left to right and returns the right most expression.
Eg:-
function a(){console.log('a'); return 'a';}
function b(){console.log('b'); return 'b';}
function c(){console.log('c'); return 'c';}
var x = (a(), b(), c());
console.log(x); // Outputs "c"
Output:-
"a"
"b"
"c"
"c"
- Note: The comma(
,) operator has the lowest priority of all javascript operators, so without the parenthesis the expression would become:(x = a()), b(), c();.
