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| -rw-r--r-- | javascript.html.markdown | 31 |
1 files changed, 31 insertions, 0 deletions
diff --git a/javascript.html.markdown b/javascript.html.markdown index 4584a28c..7fb7ba55 100644 --- a/javascript.html.markdown +++ b/javascript.html.markdown @@ -319,6 +319,37 @@ var myOtherFunc = function(){ myObj.myOtherFunc = myOtherFunc; myObj.myOtherFunc(); // = "HELLO WORLD!" +// We can also specify a context for a function to execute in when we invoke it +// using 'call' or 'apply'. + +var anotherFunc = function(s){ + return this.myString + s; +} +anotherFunc.call(myObj, " And Hello Moon!"); // = "Hello World! And Hello Moon!" + +// The 'apply' function is nearly identical, but takes an array for an argument list. + +anotherFunc.apply(myObj, [" And Hello Sun!"]); // = "Hello World! And Hello Sun!" + +// This is useful when working with a function that accepts a sequence of arguments +// and you want to pass an array. + +Math.min(42, 6, 27); // = 6 +Math.min([42, 6, 27]); // = NaN (uh-oh!) +Math.min.apply(Math, [42, 6, 27]); // = 6 + +// But, 'call' and 'apply' are only temporary. When we want it to stick, we can use +// bind. + +var boundFunc = anotherFunc.bind(myObj); +boundFunc(" And Hello Saturn!"); // = "Hello World! And Hello Saturn!" + +// Bind can also be used to partially apply (curry) a function. + +var product = function(a, b){ return a * b; } +var doubler = product.bind(this, 2); +doubler(8); // = 16 + // When you call a function with the new keyword, a new object is created, and // made available to the function via the this keyword. Functions designed to be // called like that are called constructors. |