爲什麼jquery在覆蓋的情況下需要_ $？

Question

var 
// Will speed up references to window, and allows munging its name. 
window = this, 
// Will speed up references to undefined, and allows munging its name. 
undefined, 
// Map over jQuery in case of overwrite 
_jQuery = window.jQuery, 
// Map over the $ in case of overwrite 
_$ = window.$, 

jQuery = window.jQuery = window.$ = function(selector, context) { 
    // The jQuery object is actually just the init constructor 'enhanced' 
    return new jQuery.fn.init(selector, context); 
}; 

爲什麼jQuery需要「_ $ = window. $」或「_jQuery = window.jQuery」？這對我來說沒有意義，但是如果沒有這兩行，框架就不起作用。

感謝您的幫助..

Answer 1

它保存到的$值和jQuery參考它覆蓋在他們面前，讓您可以撥打jQuery.noConflict()和恢復值。