javascript optional arguments

Arguments objectsA special variable arguments can be accessed within each function in JavaScript. This variable maintains all the list of arguments passed into this function.Note: Since arguments has been defined as a variable within a function.So by defining

We all know that JS inside the parameters of the transfer can be different, for example, we have a function: script type = "Text/javascript" > function one (a,b,c) { this .x = A; Console.log (a); } One ( 1 ); script > The number we passed was only one 1, but the formal parameter had ABC three. That's not right, is it?This time if we look at B,c, it will show undefined. PS: for example Console.log (b).Of course, there would have be

JavaScript uses the function keyword to declare functions, you can return a value with return, or you can have no return value.Recommendation: It is convenient to debug the code by either unifying the return value or not unifying the return value.function definition Format:function functionname (parameter) {//body}When defining a function, the parameters can be written or not, JavaScript does not limit the

(1) What is the difference between what is a formal parameter in a JS function and what is an argument? Parameters are called parameter variables, and the variables received by the function in JS are divided into formal parameters and arguments. An argument is a specific data that is actually used to participate in a JS function call. A formal parameter is a variable that receives an argument value when the function is called. According to the actual

About argumentsWhen calling a function, if you need to pass a parameter, the argument is an array, which can be accessed by the built-in object arguments of the function body, such as:ARGUMENTS[0]: first parameterARGUMENTS[1]: Second parameterARGUMENTS[2]: Third parameterARGUMENTS[3]: Fourth parameterOf course, in the name of the function, you can also do not need to name parameters, call arguments directly

The parameter object arguments in Javascript functions is an object, not an array. However, it can access the elements in the array through the following numeric table, and it also has the length attribute to identify the number of its elements. Use the arguments object to verify whether the function parameters are valid. Script function sum (arg1, arg2) //

(' declaring parameters ' length: ' +arguments.callee.length); Log (' Actual length: ' +arguments.length); Log ( This ); Log (p1); Log (p2); Log (p3);}functionHandlecaller () {MethodA (' xxx ', ' yyy '); Methoda.apply (Handlecaller, [' xxx ', ' yyy ']);//Specify this object}functioninit () {Handlecaller (); Methoda.call (Handlecaller,' xxx ', ' yyy ');//Specify this object}init ();Results:Notice that the first result block of this refers to the Window object, while the other two results r

For people who have learned Java, function overloading is not an unfamiliar concept, but is there a function overload in JavaScript ... And then we're going to test it.This case is modeled after the syntax in Java to simulate function overloading. Let's run the results.Alert (ON):Alert (+/-):Results comparison found that the result of the first run is Nan, and the result of the second run is normal.There is no function overload in

object in JavaScript. function Argtest (A, b) {var i, S = "The Argtest function expected";var Numargs = arguments.length; Gets the numeric value of the parameter being passed.var Expargs = argtest.length; Gets the numeric value of the expected parameter.if (Expargs S + + Expargs + "argument."ElseS + + Expargs + "arguments."if (Numargs S + + Numargs + "was passed."ElseS + + Numargs + "were passed."s + = "\

method. For the Apply method myfunction.apply (obj, arguments). Use to merge Array.prototype.concat.apply with another array ([1,2,3], arguments) The ultimate solution, directly into the real array The following code creates a new array that contains the elements in all arguments objects. var args = Array.prototype.slice.call (

Note: This article is in the original: http://www.jb51.net/article/30883.htmSelf as study, re-write.First, write in front of the wordsFront-end JavaScript programming is just a little bit of fur, Dom know a little, Jquey will use a little bit, know the solid foundation, understand the front-end of the system of Knowledge for Web development (their main do is PHP background development) important. Of course, what to use, just check what (now learn to s

(1) In the function body, the arguments array object can be used directly, and the elements of this array are all arguments actually passed in when this function is called(2) In fact, when calling a function, the number of arguments passed in can be different from the declaration of the function, the passing of different types of parameters will result in the res

For the question of whether the JavaScript function parameter is a byVal or a pass (BYREF), there is a common misconception that "simple types" such as number,string are values, number, String, Object, array, and so on "complex types." is the address.Isn't that right? Why is there such a misunderstanding? Take a look at these two pieces of code: Copy Code code as follows: //The code that creates the illusion of passing value function Modifylikeb