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This test case compares three alternative isFunction
implementations:
isFunctionA
checks the internal [[Class]]
name of an object to determine if it is a function. Unfortunately, while this check is the most reliable, it's also less efficient due to the extra call to Object#toString
.isFunctionB
was proposed as an alternative to the typeof
and instanceof
operators by Garrett Smith. This implementation uses duck-typing, so it may produce incorrect results.isFunctionC
is currently used in Underscore.js. This implementation uses only basic duck-typing; thus, it is the most likely to produce incorrect results.isFunctionS
is currently referenced in Stack Overflow in one of the unselected answers. Curious to see how it performs vs other tests.<script>
var getClass = {}.toString,
hasProperty = {}.hasOwnProperty,
expression = /Kit/g;
function Test() {}
// Checks the internal [[Class]] name of the object.
function isFunctionA(object) {
return object && getClass.call(object) == '[object Function]';
}
// Partial duck-typing implementation by Garrett Smith.
function isFunctionB(object) {
if (typeof object != 'function') return false;
var parent = object.constructor && object.constructor.prototype;
return parent && hasProperty.call(parent, 'call');
}
// Pure duck-typing implementation taken from Underscore.js.
function isFunctionC(object) {
return !!(object && object.constructor && object.call && object.apply);
}
//Typeof
function isFunctionD(object) {
return (typeof object === "function")
}
function isFunctionS(object) {
return Object.prototype.toString.call(object) == '[object Function]';
}
</script>
Ready to run.
Test | Ops/sec | |
---|---|---|
isFunctionA |
| ready |
isFunctionB |
| ready |
isFunctionC |
| ready |
isFunctionD |
| ready |
"isFunctionS" |
| ready |
You can edit these tests or add more tests to this page by appending /edit to the URL.