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[英]How to avoid observable delay in angular or make sure my function gets called only when observable is ready
[英]Understand how the anonymous function in ready gets called
我在這里只是通過這段代碼,它描述了如何在純js中創建自己的自定義ready函數。 答案被詳細解釋,我已經在js中編程了一段時間了,但是在理解代碼的初始部分時仍然有一個問題,請再次看下面的代碼:
(function(funcName, baseObj) {
// The public function name defaults to window.docReady
// but you can pass in your own object and own function name and those will be used
// if you want to put them in a different namespace
funcName = funcName || "docReady";
baseObj = baseObj || window;
var readyList = [];
var readyFired = false;
var readyEventHandlersInstalled = false;
// call this when the document is ready
// this function protects itself against being called more than once
function ready() {
if (!readyFired) {
// this must be set to true before we start calling callbacks
readyFired = true;
for (var i = 0; i < readyList.length; i++) {
// if a callback here happens to add new ready handlers,
// the docReady() function will see that it already fired
// and will schedule the callback to run right after
// this event loop finishes so all handlers will still execute
// in order and no new ones will be added to the readyList
// while we are processing the list
readyList[i].fn.call(window, readyList[i].ctx);
}
// allow any closures held by these functions to free
readyList = [];
}
}
function readyStateChange() {
if ( document.readyState === "complete" ) {
ready();
}
}
// This is the one public interface
// docReady(fn, context);
// the context argument is optional - if present, it will be passed
// as an argument to the callback
baseObj[funcName] = function(callback, context) {
// if ready has already fired, then just schedule the callback
// to fire asynchronously, but right away
if (readyFired) {
setTimeout(function() {callback(context);}, 1);
return;
} else {
// add the function and context to the list
readyList.push({fn: callback, ctx: context});
}
// if document already ready to go, schedule the ready function to run
if (document.readyState === "complete") {
setTimeout(ready, 1);
} else if (!readyEventHandlersInstalled) {
// otherwise if we don't have event handlers installed, install them
if (document.addEventListener) {
// first choice is DOMContentLoaded event
document.addEventListener("DOMContentLoaded", ready, false);
// backup is window load event
window.addEventListener("load", ready, false);
} else {
// must be IE
document.attachEvent("onreadystatechange", readyStateChange);
window.attachEvent("onload", ready);
}
readyEventHandlersInstalled = true;
}
};
})("docReady", window);
我這樣調用代碼:
docReady(function() {
alert('hello');
}, window);
我的問題是,如何像這樣調用匿名函數? ..我完全困惑:(
甚至下面的代碼如何工作?
docReady(function() {
alert('hello');
}, window);
我的意思是沒有定義明確的docReady函數,如下所示:
docReady function (param1, param2);
我所看到的只是docReady作為參數傳遞給匿名函數嗎?
baseObj[funcName] = function(callback, context) {
相當於
window["docReady"] = function(callback, context) {
它將函數聲明為window
的屬性(全局對象),這意味着您可以使用
window["docReady"](function() {
alert('hello');
}, window);
或搭配
window.docReady(function() {
alert('hello');
}, window);
甚至
docReady(function() {
alert('hello');
}, window);
因為全局對象的屬性也是全局作用域(以及陰影之前的任何內部作用域)的變量。
關鍵位是baseObj[funcName] = function
此時, baseObj
是(或至少可以是) window
, funcName
是(或可以是) docReady
。
因此,此時它向window
(全局)添加了一個名為“ docReady”的函數
window
和“ docReady”作為默認參數傳遞到最后一行
})("docReady", window);
其中在頂部將函數作為參數輸入(function(funcName, baseObj) {
NB當我說baseObj
是(或至少可以) window
,那是因為你可以重寫此值,則該行:
funcName = funcName || "docReady";
baseObj = baseObj || window;
如果未提供替代方法, baseObj
funcName
設置為“ docReady”和baseObj
,這意味着您可以根據需要更改它們,因此如果最后一行更改為})("getReady", myObject);
該函數將稱為getReady並將其添加到myObject
而不是全局window
您正在閱讀錯誤的代碼。
檢查以下行:
(function(funcName, baseObj) {
...
baseObj[funcName] = function(callback, context) {
...
};
...
})("docReady", window);
它將為baseObj
添加一個新屬性,在本例中為window
。 該屬性是您調用的函數。 docReady
。 全局的所有東西都不需要像window.something
這樣的名字。 這就是為什么您使用docReady
的原因。
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