jQuery源碼解讀之removeClass()方法分析_jquery

jQuery.fn.extend({
    removeClass: function( value ) {
        var classes, elem, cur, clazz, j, finalValue,
            i = 0,
            len = this.length,
            proceed = arguments.length === 0 || typeof value === "string" && value;
        if ( jQuery.isFunction( value ) ) {
            return this.each(function( j ) {
//這裡就是根據你傳遞的移除類別名稱的函數回傳的類別名，再次呼叫removeClass自身了。
                jQuery( this ).removeClass( value.call( this, j, this.className ) );
            });
        }
        if ( proceed ) {
            classes = ( value || "" ).match( rnotwhite ) || [];
            for ( ; i                 elem = this[ i ];
                cur = elem.nodeType === 1 && ( elem.className ?
                    ( " " elem.className " " ).replace( rclass, " " ) :
                    ""
                );
                if ( cur ) {
                    j = 0;
                    while ( (clazz = classes[j ]) ) {
//區別在下面的while循環，當檢索到目前DOM元素包含你要移除的類別名，會用replace替換成" "
                        while ( cur.indexOf( " " clazz " " ) >= 0 ) {
                            cur = cur.replace( " "clazz" ", " " );
                        }
                    }
//下面也是關鍵區別之一，判斷你是否傳遞了要移除的類別名稱value。如果沒有傳遞，則finalValue=""，如果此時DOM元素有類別名稱的話，也就是條件為true，移除DOM元素的所有類別名稱；
//如果傳遞了，則移除符合的類別名，移除後，沒有移除的類別名稱拼接成了cur，去掉左右兩端的空格字串，將DOM元素的類別名稱設為cur。
                    finalValue = value ? jQuery.trim( cur ): "";
                    if ( elem.className !== finalValue ) {
                        elem.className = finalValue;
                    }
                }
            }
        }
        return this;
    }
});