Content deleted Content added
m →Type conversion: fancy quotes |
→Type conversion: add anchor and bold |
||
Line 381:
;{{small|Boolean}}: If one of the operands is a Boolean, the Boolean operand is converted to 1 if it is {{mono|true}}, or to 0 if it is {{mono|false}}.
;{{small|Object}}: If an object is compared with a number or string, JavaScript attempts to return the default value for the object. An object is converted to a primitive String or Number value, using the {{mono|.valueOf()}} or {{mono|.toString()}} methods of the object. If this fails, a runtime error is generated.
{{anchor|truthy and falsy}}
[[Douglas Crockford]] advocates the terms "'''truthy'''" and "'''falsy'''" to describe how values of various types behave when evaluated in a logical context, especially in regard to edge cases.<ref>{{cite web | url=http://javascript.crockford.com/style2.html | title=The Elements of JavaScript Style | publisher=Douglas Crockford | access-date=5 March 2011}}</ref>
The binary logical operators returned a Boolean value in early versions of JavaScript, but now they return one of the operands instead. The left–operand is returned, if it can be evaluated as : {{mono|false}}, in the case of [[logical conjunction|conjunction]]: (<code>a && b</code>), or {{mono|true}}, in the case of [[logical disjunction|disjunction]]: (<code>a || b</code>); otherwise the right–operand is returned. Automatic type coercion by the comparison operators may differ for cases of mixed Boolean and number-compatible operands (including strings that can be evaluated as a number, or objects that can be evaluated as such a string), because the Boolean operand will be compared as a numeric value. This may be unexpected. An expression can be explicitly cast to a Boolean primitive by doubling the logical [[negation|negation operator]]: ({{mono|!!}}), using the {{mono|Boolean()}} function, or using the [[Conditional (programming)|conditional operator]]: (<code>c ? t : f</code>).
| |||