what do && and || mean in the following code : <p>Reading highstock source codes, but confused the following codes:</p>

<pre><code>textLineHeight = textStyles &amp;&amp; textStyles.lineHeight,

wrapper.height = (height || bBox.height || 0) + 2 * padding;

cHeight = (old &amp;&amp; chart.oldChartHeight) || chart.chartHeight;
</code></pre>

<p>Thanks</p>
