201506170744_ JavaScript authoritative Guide (sixth edition)-function call variable length arguments and optional parameters, "(p171-175)

I. Constructor call (with or without return)

1. var obj = new Object ();

var obj = new Object;

The two lines of code are equivalent; expression: New obj.m ();, this is not obj!!

The constructor is usually not used with the return keyword;

Two. Indirect calls

1. Call (), and apply (); Function: Any object can call any method/

Call ();--use its own arguments as arguments to the function;

Apply ();--to pass in an argument as an array;

2. Optional parameter: var a = a | | [];

3. Variable-length arguments: Arguments is a reference to an argument;

For example:

function Add (a,b,c) {

if (arguments.length! = 3) {

throw new Error ("The number of arguments actually passed in is:" + Arguments.length + ", but the function defines the number of formal parameters is 3!) ");

}else{

Return a + B + C

}

};

Add (1,1,2,9); Error: The actual number of arguments passed in is: 4, but the function defines the number of formal parameters is 3!

3. Function Add (a,b,c) {if (arguments.length! = 3) {throw new Error ("The number of arguments actually passed in is:" + Arguments.length + ", but the function defines the number of formal parameters is 3!) ");} Else{arguments[0] = Null;return A + B + c}};  Add (9,.); The result is: 3. "9" is set to "null" value;

4. Arguments in strict mode it cannot be assigned, and cannot be used as a reserved word for formal parameter names.

5.

201506170744_ JavaScript authoritative Guide (sixth edition)-function call variable length arguments and optional parameters, "(p171-175)