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copied!<p>Your real question seem to be:</p> <p>Why:</p> <pre><code>null >= 0; // true </code></pre> <p>But:</p> <pre><code>null == 0; // false </code></pre> <p>What really happens is that the <em>Greater-than-or-equal Operator</em> (<code>>=</code>), performs type coercion (<a href="http://www.ecma-international.org/ecma-262/5.1/#sec-9.1" rel="noreferrer"><code>ToPrimitive</code></a>), with a <em>hint</em> type of <code>Number</code>, actually all the relational operators have this behavior.</p> <p><code>null</code> is treated in a special way by the <em>Equals Operator</em> (<code>==</code>). In a brief, it only <em>coerces</em> to <code>undefined</code>:</p> <pre><code>null == null; // true null == undefined; // true </code></pre> <p>Value such as <code>false</code>, <code>''</code>, <code>'0'</code>, and <code>[]</code> are subject to numeric type coercion, all of them coerce to zero.</p> <p>You can see the inner details of this process in the <a href="http://www.ecma-international.org/ecma-262/5.1/#sec-11.9.3" rel="noreferrer">The Abstract Equality Comparison Algorithm</a> and <a href="http://www.ecma-international.org/ecma-262/5.1/#sec-11.8.5" rel="noreferrer">The Abstract Relational Comparison Algorithm</a>.</p> <p>In Summary: </p> <ul> <li><p>Relational Comparison: if both values are not type String, <code>ToNumber</code> is called on both. This is the same as adding a <code>+</code> in front, which for null coerces to <code>0</code>. </p></li> <li><p>Equality Comparison: only calls <code>ToNumber</code> on Strings, Numbers, and Booleans.</p></li> </ul>

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