Traditional and Modern events in javascript, modern javascript

Traditional and Modern events in javascript, modern javascript

As we all know, the modern event binding (attachEvent) in IE has many problems compared with the W3C standard (addEventListener,

For example, a memory leak occurs, and events are repeatedly added and triggered in reverse mode.

The following describes how to bind an encapsulated event to a traditional event:

AddEvent. ID = 1; // event counter function addEvent (obj, type, fn) {if (obj. addEventListener) {obj. addEventListener (type, fn, false);} else {// IE // determines whether the object exists. Ensure that only one object exists. Otherwise, each execution is performed, creates an event object // an array of Storage types and functions in the form of key-value pairs, ======== mount the event object array to the obj object to facilitate event deletion if (! Obj. events) {// Equivalent Structure: obj. events: {click: [fn1, fn2], mouserover: [fn1],...} obj. events ={};} var flag = false; // store the event object if (! Obj. events [type]) {// type data storage function obj. events [type] = []; // The first event type and function of this type are stored in the first obj of this type array. events [type] [0] = fn;} else {var eventfn = obj. events [type]; // cyclically traverse this type of object to check whether the event is repeated. If the repeated flag is true, return for (var I in eventfn) {if (eventfn [I] = fn) {flag = true; return ;}}// you can check whether the event is repeated. if the event is repeated, no function is stored, otherwise, save the event and execute if (! Flag) {// when this type already exists, the accumulative time type function is stored for this event, and eventfn [addEvent is executed cyclically. ID ++] = fn ;}// event function type Array function traversal call obj ["on" + type] = function () {var event = window. event; // store the event object // Add a function after the event object, call it when executed, and prevent the occurrence of default behavior, and synchronize the event with W3C standard. preventDefault = function () {this. returnValue = false ;}; // Add a function after the event object, a tail function, and stop bubbling. Event. stopPropagation = function () {this. cancelBubble = true ;}; // multiple functions of the execution type stored in cyclic traversal var evfn = obj. events [type]; for (var I in evfn) {// sequentially execute this type of event function, it solves the problem of coverage of traditional events and reverse triggering events bound to modern events. evfn [I]. call (this, event); // place the execution function in the environment of this object for execution, and pass an event object to the function callback using function removeEvent (obj, type, fn) {if (obj. removeEventListener) {obj. removeEventListener (type, fn, false);} else {// cyclically traverses this type of event function under this object, if yes, delete the event function var evefn = obj. events [type]; for (var I in evefn) {if (evefn [I] = fn) {// delete evefn [I]; this method can also delete the entry of the array, but will retain the value of undefined evefn when accessing the location. splice (I, 1); // delete 1 digit from position I ,}}}}

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