Actionscript 2 error if statement

I am trying to create a if statement, but I get this compolor error:

')' expected
Unexpected '}' encountered

My function:

function hideThumbs():Void {
    contentHolder.thumbHolder._visible = false;
        if (contentHolder.testerHolder._visible = true;) {
        contentHolder.testerHolder._visible = false;
    } else {
        }
    //contentHolder.thumbHolder.alphaTo(0, buttonTime,开发者_运维技巧 menuTween, 0, function(){ moveThumbs("out"); });
    //thumbsHidden = true;
}

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Did you try:

if (contentHolder.testerHolder._visible == true) {

The semicolon has nothing to do there, and you want a comparison operator in there, not an assignment.