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2.1.35 [ECMA-262-1999] Section 11.9.3, The Abstract Equality Comparison Algorithm

V0052:

The comparison x == y, where x and y are values, produces true or false. Such a comparison is performed as follows:

(The bulleted steps are added before step 1)

  • __If Type(x) is SafeArray or Type(y) is SafeArray, return false.__

  • __If Type(x) is VarDate or Type(y) is VarDate, return false.__

  1. If Type(x) is different from Type(y), go to step 14.

  2. If Type(x) is Undefined, return true.

  3. If Type(x) is Null, return true.

  4. If Type(x) is not Number, go to step 11.

  5. If x is NaN, return false.

  6. If y is NaN, return false.

  7. If x is the same number value as y, return true.

  8. If x is +0 and y is -0, return true.

  9. If x is -0 and y is +0, return true.

  10. Return false.

  11. 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.

  12. If Type(x) is Boolean, return true if x and y are both true or are both false. Otherwise, return false.

  13. Return true if x and y refer to the same object or if they refer to objects joined to each other (see [ECMA-262-1999] section 13.1.2). Otherwise, return false.

  14. If x is null and y is undefined, return true.

  15. If x is undefined and y is null, return true.

  16. If Type(x) is Number and Type(y) is String, return the result of the comparison x == ToNumber(y).

  17. If Type(x) is String and Type(y) is Number, return the result of the comparison ToNumber(x) == y.

  18. If Type(x) is Boolean, return the result of the comparison ToNumber(x) == y.

  19. If Type(y) is Boolean, return the result of the comparison x == ToNumber(y).

  20. If Type(x) is either String or Number and Type(y) is Object, return the result of the comparison x == ToPrimitive(y).

  21. If Type(x) is Object and Type(y) is either String or Number, return the result of the comparison ToPrimitive(x) == y.

  22. Return false.

For JScript 5.x, if either x or y is a host object then the "same object" determination in step 13 is implementation defined and dependent upon characteristics of the specific host objects. The method of determination used may be different from the "same object" determination made in step 13 of the Strict Equality Comparison Algorithm ([ECMA-262-1999] section 11.9.6). If x or y are host objects then interchanging their values may produce a different result.