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  1. PO
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    <p>The behavior of == is a bit lengthy, but clearly defined in the <a href="http://www.ecma-international.org/publications/standards/Ecma-262.htm" rel="noreferrer">ecma-262 spec</a>:</p> <blockquote> <p>11.9.3 The Abstract Equality Comparison Algorithm</p> <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>If Type(x) is different from Type(y), go to step 14.</li> <li>If Type(x) is Undefined, return true.</li> <li>If Type(x) is Null, return true.</li> <li>If Type(x) is not Number, go to step 11.</li> <li>If x is NaN, return false.</li> <li>If y is NaN, return false.</li> <li>If x is the same number value as y, return true.</li> <li>If x is +0 and y is −0, return true.</li> <li>If x is −0 and y is +0, return true.</li> <li>Return false.</li> <li>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.</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 or if they refer to objects joined to each other (see 13.1.2). Otherwise, return false.</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> <p>Step 16 applies to your former example:</p> <pre><code> 0 == "0" // apply 16 ≡ 0 == toNumber("0") ≡ 0 == 0 // apply 7 ≡ true </code></pre> <p>And step 18, then step 16, apply to the latter:</p> <pre><code> true == "true" // apply 18 ≡ toNumber(true) == "true" ≡ 1 == "true" // apply 16 ≡ 1 == toNumber("true") ≡ 1 == NaN // apply 6 ≡ false </code></pre>
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    1. POIn Javascript, <int-value> == "<int-value>" evaluates to true. Why is it so?
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    1. USAndrey Fedorov
    1. USAndrey Fedorov
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    1. POIn Javascript, <int-value> == "<int-value>" evaluates to true. Why is it so?
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    1. CO+0.8 for the great answer, +0.2 for finding the ≡ character
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      1. USnickf
    2. COvery nice indeed. you answered both questions well.
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      1. USReal Red.
    3. COI think this is my first accepted answer, thanks guys! :)
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      1. USAndrey Fedorov
 

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