Are there other ways to increment a for
loop in Javascript besides i++
and ++i
? For example, I want to increment by 3 instead of one.
for (var i = 0; i < myVar.length; i+3) {
//every three
}
This question is related to
javascript
for-loop
increment
The last part of the ternary operator allows you to specify the increment step size. For instance, i++ means increment by 1. i+=2 is same as i=i+2,... etc. Example:
let val= [];
for (let i = 0; i < 9; i+=2) {
val = val + i+",";
}
console.log(val);
Expected results: "2,4,6,8"
'i' can be any floating point or whole number depending on the desired step size.
for (var i = 0; i < 10; i = i + 2) {
// code here
}?
You certainly can. Others have pointed out correctly that you need to do i += 3
. You can't do what you have posted because all you are doing here is adding i + 3
but never assigning the result back to i
. i++
is just a shorthand for i = i + 1
, similarly i +=3
is a shorthand for i = i + 3
.
There is an operator just for this. For example, if I wanted to change a variable i by 3 then:
var someValue = 9;
var Increment = 3;
for(var i=0;i<someValue;i+=Increment){
//do whatever
}
_x000D_
var someValue = 3;
var Increment = 3;
for(var i=9;i>someValue;i+=Increment){
//do whatever
}
_x000D_
for (var i = 0; i < myVar.length; i+=3) {
//every three
}
additional
Operator Example Same As
++ X ++ x = x + 1
-- X -- x = x - 1
+= x += y x = x + y
-= x -= y x = x - y
*= x *= y x = x * y
/= x /= y x = x / y
%= x %= y x = x % y
A for
loop:
for(INIT; TEST; ADVANCE) {
BODY
}
Means the following:
INIT;
while (true) {
if (!TEST)
break;
BODY;
ADVANCE;
}
You can write almost any expression for INIT
, TEST
, ADVANCE
, and BODY
.
Do note that the ++
operators and variants are operators with side-effects (one should try to avoid them if you are not using them like i+=1
and the like):
++i
means i+=1; return i
i++
means oldI=i; i+=1; return oldI
Example:
> i=0
> [i++, i, ++i, i, i--, i, --i, i]
[0, 1, 2, 2, 2, 1, 0, 0]
Andrew Whitaker's answer is true, but you can use any expression for any part.
Just remember the second (middle) expression should evaluate so it can be compared to a boolean true
or false
.
When I use a for
loop, I think of it as
for (var i = 0; i < 10; ++i) {
/* expression */
}
as being
var i = 0;
while( i < 10 ) {
/* expression */
++i;
}
Source: Stackoverflow.com