javascript对象原型调用
[英]javascript object prototype call
问题描述
b2 and b3 are not triggering the prototype functions and no errors are generated? 
b2和b3没有触发原型功能，没有产生错误？ How does one accomplish calling prototype functions in the fashion? 如何以时尚方式完成调用原型函数？
<html> <head> <script type="text/javascript"> function newObj(){ this.obj_val= 7; } var trigger_f0 = function(){ alert("here 0"); // trigger FINE! (ok) } newObj.prototype.trigger_f2 = function (){ // no triggering off click event alert("here 2"); } newObj.prototype.trigger_f3 = function (){ // not triggering off click event alert("obj value:" + newObj.obj_val); } var init = function(){ b3.addEventListener('click', newObj.trigger_f3, false); b2.addEventListener('click', newObj.trigger_f2, false); b1.addEventListener('click', trigger_f0, false); } window.addEventListener('DOMContentLoaded', init, false); </script> </head> <body> <button id="b1">B1</button> <button id="b2">B2</button> <button id="b3">B3</button> </body> </html>
2 个解决方案
解决方案1
2 2017-03-12 20:52:05
You need to create an instance like to get an object out of the constructor function 您需要创建一个实例，以便从构造函数中获取对象
var a=new newObj()
and then access the properties. 然后访问属性。 and change newObj.obj_val to 并将newObj.obj_val更改为
new newObj().obj_val
function newObj() { this.obj_val = 7; } var trigger_f0 = function() { alert("here 0"); // trigger FINE! (ok) } newObj.prototype.trigger_f2 = function() { // no triggering off click event alert("here 2"); } newObj.prototype.trigger_f3 = function() { // not triggering off click event alert("obj value:" + new newObj().obj_val); } var a = new newObj(); b3.addEventListener('click', a.trigger_f3, false); b2.addEventListener('click', a.trigger_f2, false); b1.addEventListener('click', trigger_f0, false);
<body> <button id="b1">B1</button> <button id="b2">B2</button> <button id="b3">B3</button> </body>
解决方案2
0 2017-03-13 05:26:24
When you create a function and add properties to its .prototype , the function doesn't receive them. 当您创建函数并向其.prototype添加属性时，该函数不会接收它们。
Instead, when you create an instance/object using that function as constructor, that object will get the functions. 相反，当您使用该函数作为构造函数创建实例/对象时，该对象将获得函数。
function foo() {}
foo.prototype.fn = function(){}
var x = new foo()
console.log(foo.fn) // undefined
console.log(x.fn) // function (){}
In your case, 在你的情况下，
// ...
var obj = newObj();
var init = function(){
b3.addEventListener('click', obj.trigger_f3, false);
b2.addEventListener('click', obj.trigger_f2, false);
b1.addEventListener('click', trigger_f0, false);
}
window.addEventListener('DOMContentLoaded', init, false);
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