javascript - objects unable to change its own member's values -

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i have created object type has member x , y, functions changing members' value. have seen members been changed in debugger. none of members changed. can explain? there difference in behaviour of x , y? 1 local variable , other parameter.

<!doctype html> <html xmlns="http://www.w3.org/1999/xhtml"> <head>     <title></title> </head> <body>     <div id="debug"></div>     <script src="scripts/jquery-2.0.0.min.js"></script>     <script>         function a(y) {             var x = 0;             return {                 x: x,                 y: y,                 getx: getx,                 gety: gety,                 processx: processx,                 processy: processy,             }             function getx() {                 return x;             }             function gety() {                 return y;             }             function processx() {                 this.x = 1;             }             function processy() {                 this.y = 100;             }         }         $(function () {             var objs = [];             (var = 0; < 3; i++) {                 objs[i] = a(i);             }             objs[0].processx();             objs[1].processy();             objs.foreach(function (o) {                 $("#debug").append($("<p>").text(o.x + " " + o.y));                 $("#debug").append($("<p>").text(o.getx() + " " + o.gety())); //result: //1 0 //0 0 //0 100 //0 1 //0 2 //0 2             });         });     </script> </body> </html>

strangely if write function access members, correct values can obtained. why???

you have explicitly involve this when want modify object properties:

        function getx() {             return this.x;         }         function gety() {             return this.y;         }         function processx() {             this.x = 1;         }         function processy() {             this.y = 100;         }

in original code, references "x" , "y" inside 4 functions resolved local variables "x" , "y" inside outer function (the function called "a"). "a" function includes parameter called "y" , var declaration "x".


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