What does this *= symbol mean in Javascript?
<p>I am currently reading Eloquent Javascript, and this keeps coming up: </p>

<p><code>*=</code></p>

<p>in context: </p>

<pre><code>function power(base, exponent) {
    if (exponent == undefined)
        exponent = 2;
    var result = 1;
    for (var count = 0; count &lt; exponent; count++)
        result *= base;
    return result;
}

console.log(power(4));
// → 16
console.log(power(4, 3));
// → 64
</code></pre>

<p>I'm a beginner so please explain as if I were a 5 year old (not too far off). Thank you</p>