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    <h2>Human readable text about their differences</h2> <p>Using <code>!==</code> and <code>===</code> will do a more strict compare than <code>==</code>/<code>!=</code>. The former will check if the objects being compared are of the same type, as well as if the values matches.</p> <p>Using <code>==</code> will make it possible for an implicit cast to be made, see the below examples.</p> <pre><code>(0 == '0') // true (0 === '0') // false ('' == 0 ) // true, the string will implicitly be converted to an integer ('' === 0 ) // false, no implicit cast is being made </code></pre> <hr> <h2>What does the standard say?</h2> <blockquote> <h2>11.9.6 The Strict Equality Comparison</h2> <p>Algorithm The comparison x === y, where x and y are values, produces true or false. Such a comparison is performed as follows:</p> <ol> <li>If Type(x) is different from Type(y), return false.</li> <li>If Type(x) is Undefined, return true.</li> <li>If Type(x) is Null, return true.</li> <li><p>If Type(x) is Number, then</p> <p>a. If x is NaN, return false.</p> <p>b.If y is NaN, return false.</p> <p>c. If x is the same Number value as y, return true.</p> <p>d. If x is +0 and y is 0, return true.</p> <p>e. If x is 0 and y is +0, return true.</p> <p>f. Return false.</p></li> <li><p>If Type(x) is String, then return true if x and y are exactly the same sequence of characters (same length and same characters in corresponding positions); otherwise, return false.</p></li> <li>If Type(x) is Boolean, return true if x and y are both true or both false; otherwise, return false.</li> <li>Return true if x and y refer to the same object. Otherwise, return false. NOTE This algorithm differs from the SameValue Algorithm (9.12) in its treatment of signed zeroes and NaNs.</li> </ol> </blockquote> <hr> <blockquote> <h3>11.9.3 The Abstract Equality Comparison Algorithm</h3> <p>The comparison x == y, where x and y are values, produces true or false. Such a comparison is performed as follows:</p> <ol> <li><p>If Type(x) is the same as Type(y), then</p> <p>a. If Type(x) is Undefined, return t rue.</p> <p>b. If Type(x) is Null, return true.</p> <p>c. If Type(x) is Number, then</p> <pre><code>1. If x is NaN, return false. 2. If y is NaN, return false. 3. If x is the same Number value as y, return true. 4. If x is +0 and y is 0, return true. 5. If x is 0 and y is +0, return true. 6. Return false. </code></pre> <p>d. If Type(x) is String, then return true if x and y are exactly the same sequence of characters (same length and same characters in corresponding positions). Otherwise, return false.</p> <p>e. If Type(x) is Boolean, return true if x and y are both true or both false. Otherwise, return false. f. Return true if x and y refer to the same object. Otherwise, return false.</p></li> <li>If x is null and y is undefined, return true.</li> <li>If x is undefined and y is null, return true.</li> <li>If Type(x) is Number and Type(y) is String, return the result of the comparison x == ToNumber(y).</li> <li>If Type(x) is String and Type(y) is Number, return the result of the comparison ToNumber(x) == y.</li> <li>If Type(x) is Boolean, return the result of the comparison ToNumber(x) == y.</li> <li>If Type(y) is Boolean, return the result of the comparison x == ToNumber(y).</li> <li>If Type(x) is either String or Number and Type(y) is Object, return the result of the comparison x == ToPrimitive(y) .</li> <li>If Type(x) is Object and Type(y) is either String or Number, return the result of the comparison ToPrimitive(x) == y.</li> <li>Return false</li> </ol> </blockquote>
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