javascript--the reference pass of the object argument

Today, there is a problem, how to affect the parameter changes outside the function, such as:

<Script>    varmyname= "Wood";    A (myname);    document.write (myname); functionA (n) {n= "Yao"; }</Script>

The output is also wood, which shows that when myname passes in a function, it is equivalent to having a copy of the myname in the body of the function, the value of which is equal to myname, and what is done to it in the function body is performed on that copy.

But the situation is different, when the passed parameter is an array, an object , changes to the parameters in the function body are reflected on the original variable.

<Script>    varmyname= ["Wood"];    A (myname); document.write (myname[0]); functionA (n) {n[0] = "Yao"; }</Script>

As you can see, the first element of the Friut array has been changed in the above code.

Here is an example of an object:

<Script>    varmyname={name1:"Wood"};    A (myname);    document.write (MYNAME.NAME1); functionA (n) {n.name1= "Yao"; }</Script>

It is obvious that the changes in the parameters of the function body affect the original variable, which is different from the usual parameter. Special attention is required.

But, when assigning a value to an incoming array or object in the body of a function, the change is not reflected in the original variable outside the function body!

Please see:

<Script>    varmyname={name1:"Wood"};    A (myname);    document.write (MYNAME.NAME1); functionA (n) {n={name1:"Yao"}; }</Script>

You must think that the value of the MyName variable's Name1 property has been changed to ' Yao ' after executing a (), as the changes inside the above function reflect the theory of the original variable. But the results are a bit hard to accept.

The reason for this is that when an assignment is used within a function body, a variable named P is created. This p is a variable inside the function, it is assigned to the function in the body of course, the outside of the myname is still the original myname.

The difference between this step and the original code is whether the parameter is assigned a new value in the body of the function, or the property of the parameter or the element of the array is changed .

Here we re-implement the example of a clock number format output by passing the object:

<Script>    varMyTime=Self.setinterval (function() {getTime (); },  +); //alert ("OK");    functionGetTime () {varTimer= NewDate (); varT={h:timer.gethours (), M:timer.getminutes (), S:timer.getseconds () }            //The time object T, passed into the function checktime (), changes the value in the object directly in Checktime ().             //Without having to receive the return value and then assign a valuechecktime (t); document.getElementById ("Timer"). InnerHTML=t.h+ ":" +T.M+ ":" +T.s; }    functionChecktime (i) {if(i.h< Ten) {i.h= "0" +i.h; }        if(I.M< Ten) {I.M= "0" +I.M; }        if(I.s< Ten) {I.s= "0" +I.s; }    }</Script>

The example uses the SetInterval () function to periodically invoke a refresh event, or it can be implemented by recursive invocation of settimeout () in gettime ().

javascript--the reference pass of the object argument