Warnings:

• The operand to the left of the operator must be an LValue. That is, it should be able to take an assignment and store the value.

• Be careful not to confuse the single equals with the double equals. Placing a double equals in place of an assignment will not assign the value and may be considered to be a syntax error, since it may perform a comparison in entirely the wrong context. The interpreter may be forgiving enough that a run-time error isn't generated though, but the side effects could be subtle and make it hard to diagnose the cause.

Cross-references:

ECMA 262 edition 2 - section - 11.13

ECMA 262 edition 2 - section - 12.2

ECMA 262 edition 3 - section - 11.13

ECMA 262 edition 3 - section - 12.2