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4.13.5 The Comma Operator (,)

This HTML could be more cleanly written using an onclick event handler rather than a javascript:URL, of course, and the voidoperator would not be necessary in that case.


4.13.5 The Comma Operator (,)

The comma operator is a binary operator whose operands may be of any type. It evaluates its left operand, evaluates its right operand, and then returns the value of the right operand. Thus, the following line:

i=0, j=1, k=2;

evaluates to 2 and is basically equivalent to:

i = 0; j = 1; k = 2;

The left-hand expression is always evaluated, but its value is discarded, which means that it only makes sense to use the comma operator when the left-hand expression has side effects. The only situation in which the comma operator is commonly used is with a for loop ( §5.5.3 ) that has multiple loop variables:

// The first comma below is part of the syntax of the var statement

// The second comma is the comma operator: it lets us squeeze 2

// expressions (i++ and j--) into a statement (the for loop) that expects 1.

for(var i=0,j=10; i < j; i++,j--)

console.log(i+j);

4.13 Miscellaneous Operators | 85

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