[RESOLVED] Checkbox

The code below is executed when a checkbox (A0) is clicked on, however it causes the checkbox to not be checked and doesn't change when it's clicked on again. Why is this?

Code:

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if (document.getElementById("courseA0").checked = false) {
                document.getElementById("courseM0").disabled = false;
                document.getElementById("courseG0").disabled = false;
}

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Change the test with a comparison operator (==) and not an assignment operator (=) !

Code:

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if (document.getElementById("courseA0").checked == false) {
                document.getElementById("courseM0").disabled = false;
                document.getElementById("courseG0").disabled = false;
}

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Thank you.