Multi variable for loop Java Script

Question

Is there any way, below code works properly.. i want 'i' to stop when the limit is reached .. without using an if condition

var a1 = [1, 2, 3, 4, 5, 6];
var a2 = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
for (var i = 0, j = 0; i < a1.length, j < a2.length; i++, j++) {
 console.log('a1: ' + '[' + i + ']' + a1[i]);
 console.log('a2: ' + a2[j]);
}

• Nina Scholz: is there any special reason for using two counters with the same content?
• Basilin Joe: No special reasons,other than am lazy

Answer 1

The second parameter of a loop should be a boolean condition.

This one

i < a1.length, j < a2.length

is actually interpreted in such way that it returns the result of i < a1.length only.

Since you want the loop to execute while both of conditions are true, combine these conditions using logical AND operator:

var a1 = [1, 2, 3, 4, 5, 6];
var a2 = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
for (var i = 0, j = 0; i < a1.length && j < a2.length; i++, j++) {
 console.log('a1: ' + '[' + i + ']' + a1[i]);
 console.log('a2: ' + a2[j]);
}

By the way, i and j are actually duplicating each other. You may use the single loop counter:

var a1 = [1, 2, 3, 4, 5, 6];
var a2 = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
for (var i = 0; i < a1.length && i < a2.length; i++) {
 console.log('a1: ' + '[' + i + ']' + a1[i]);
 console.log('a2: ' + a2[i]);
}

or even

var a1 = [1, 2, 3, 4, 5, 6];
var a2 = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
var minLength = Math.min(a1.length, a2.length);
for (var i = 0; i < minLength; i++) {
 console.log('a1: ' + '[' + i + ']' + a1[i]);
 console.log('a2: ' + a2[i]);
}

• Basilin Joe: Thing is ,i need ' j ' to go till 10
• Yeldar Kurmangaliyev: @CodeBean There is no convenient and proper way to do this using for loop without if condition. Moreover, there is not so much sense. However, you may implement it using while.

Answer 2

no need for if condition

var a1 = [1, 2, 3, 4, 5, 6];
var a2 = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
for (var i = 0, j = 0; i < a1.length, j < a2.length, a1[i]; i++, j++) {
 console.log('a1: ' + '[' + i + ']' + a1[i]);
 console.log('a2: ' + a2[j]);
}