读jQuery源码之三

jQuery.extend = jQuery.fn.extend = function() {
    var options, name, src, copy, copyIsArray, clone,
        target = arguments[0] || {},
        i = 1,
        length = arguments.length,
        deep = false;

    // Handle a deep copy situation
    if ( typeof target === "boolean" ) {
        deep = target;

        // Skip the boolean and the target
        target = arguments[ i ] || {};
        i++;
    }

    // Handle case when target is a string or something (possible in deep copy)
    if ( typeof target !== "object" && !jQuery.isFunction(target) ) {
        target = {};
    }

    // Extend jQuery itself if only one argument is passed
    if ( i === length ) {
        target = this;
        i--;
    }

    for ( ; i < length; i++ ) {
        // Only deal with non-null/undefined values
        if ( (options = arguments[ i ]) != null ) {
            // Extend the base object
            for ( name in options ) {
                src = target[ name ];
                copy = options[ name ];

                // Prevent never-ending loop
                if ( target === copy ) {
                    continue;
                }

                // Recurse if we‘re merging plain objects or arrays
                if ( deep && copy && ( jQuery.isPlainObject(copy) || (copyIsArray = jQuery.isArray(copy)) ) ) {
                    if ( copyIsArray ) {
                        copyIsArray = false;
                        clone = src && jQuery.isArray(src) ? src : [];

                    } else {
                        clone = src && jQuery.isPlainObject(src) ? src : {};
                    }

                    // Never move original objects, clone them
                    target[ name ] = jQuery.extend( deep, clone, copy );

                // Don‘t bring in undefined values
                } else if ( copy !== undefined ) {
                    target[ name ] = copy;
                }
            }
        }
    }

    // Return the modified object
    return target;
};

jQuery.extend({
    // Unique for each copy of jQuery on the page
    expando: "jQuery" + ( version + Math.random() ).replace( /\D/g, "" ),

    // Assume jQuery is ready without the ready module
    isReady: true,

    error: function( msg ) {
        throw new Error( msg );
    },

    noop: function() {},

    isFunction: function( obj ) {
        return jQuery.type(obj) === "function";
    },

    isArray: Array.isArray,

    isWindow: function( obj ) {
        return obj != null && obj === obj.window;
    },

    isNumeric: function( obj ) {
        // parseFloat NaNs numeric-cast false positives (null|true|false|"")
        // ...but misinterprets leading-number strings, particularly hex literals ("0x...")
        // subtraction forces infinities to NaN
        // adding 1 corrects loss of precision from parseFloat (#15100)
        return !jQuery.isArray( obj ) && (obj - parseFloat( obj ) + 1) >= 0;
    },

    isPlainObject: function( obj ) {
        // Not plain objects:
        // - Any object or value whose internal [[Class]] property is not "[object Object]"
        // - DOM nodes
        // - window
        if ( jQuery.type( obj ) !== "object" || obj.nodeType || jQuery.isWindow( obj ) ) {
            return false;
        }

        if ( obj.constructor &&
                !hasOwn.call( obj.constructor.prototype, "isPrototypeOf" ) ) {
            return false;
        }

        // If the function hasn‘t returned already, we‘re confident that
        // |obj| is a plain object, created by {} or constructed with new Object
        return true;
    },

    isEmptyObject: function( obj ) {
        var name;
        for ( name in obj ) {
            return false;
        }
        return true;
    },

    type: function( obj ) {
        if ( obj == null ) {
            return obj + "";
        }
        // Support: Android<4.0, iOS<6 (functionish RegExp)
        return typeof obj === "object" || typeof obj === "function" ?
            class2type[ toString.call(obj) ] || "object" :
            typeof obj;
    },

    // Evaluates a script in a global context
    globalEval: function( code ) {
        var script,
            indirect = eval;

        code = jQuery.trim( code );

        if ( code ) {
            // If the code includes a valid, prologue position
            // strict mode pragma, execute code by injecting a
            // script tag into the document.
            if ( code.indexOf("use strict") === 1 ) {
                script = document.createElement("script");
                script.text = code;
                document.head.appendChild( script ).parentNode.removeChild( script );
            } else {
            // Otherwise, avoid the DOM node creation, insertion
            // and removal by using an indirect global eval
                indirect( code );
            }
        }
    },

    // Convert dashed to camelCase; used by the css and data modules
    // Support: IE9-11+
    // Microsoft forgot to hump their vendor prefix (#9572)
    camelCase: function( string ) {
        return string.replace( rmsPrefix, "ms-" ).replace( rdashAlpha, fcamelCase );
    },

    nodeName: function( elem, name ) {
        return elem.nodeName && elem.nodeName.toLowerCase() === name.toLowerCase();
    },

    // args is for internal usage only
    each: function( obj, callback, args ) {
        var value,
            i = 0,
            length = obj.length,
            isArray = isArraylike( obj );

        if ( args ) {
            if ( isArray ) {
                for ( ; i < length; i++ ) {
                    value = callback.apply( obj[ i ], args );

                    if ( value === false ) {
                        break;
                    }
                }
            } else {
                for ( i in obj ) {
                    value = callback.apply( obj[ i ], args );

                    if ( value === false ) {
                        break;
                    }
                }
            }

        // A special, fast, case for the most common use of each
        } else {
            if ( isArray ) {
                for ( ; i < length; i++ ) {
                    value = callback.call( obj[ i ], i, obj[ i ] );

                    if ( value === false ) {
                        break;
                    }
                }
            } else {
                for ( i in obj ) {
                    value = callback.call( obj[ i ], i, obj[ i ] );

                    if ( value === false ) {
                        break;
                    }
                }
            }
        }

        return obj;
    },

    // Support: Android<4.1
    trim: function( text ) {
        return text == null ?
            "" :
            ( text + "" ).replace( rtrim, "" );
    },

    // results is for internal usage only
    makeArray: function( arr, results ) {
        var ret = results || [];

        if ( arr != null ) {
            if ( isArraylike( Object(arr) ) ) {
                jQuery.merge( ret,
                    typeof arr === "string" ?
                    [ arr ] : arr
                );
            } else {
                push.call( ret, arr );
            }
        }

        return ret;
    },

    inArray: function( elem, arr, i ) {
        return arr == null ? -1 : indexOf.call( arr, elem, i );
    },

    merge: function( first, second ) {
        var len = +second.length,
            j = 0,
            i = first.length;

        for ( ; j < len; j++ ) {
            first[ i++ ] = second[ j ];
        }

        first.length = i;

        return first;
    },

    grep: function( elems, callback, invert ) {
        var callbackInverse,
            matches = [],
            i = 0,
            length = elems.length,
            callbackExpect = !invert;

        // Go through the array, only saving the items
        // that pass the validator function
        for ( ; i < length; i++ ) {
            callbackInverse = !callback( elems[ i ], i );
            if ( callbackInverse !== callbackExpect ) {
                matches.push( elems[ i ] );
            }
        }

        return matches;
    },

    // arg is for internal usage only
    map: function( elems, callback, arg ) {
        var value,
            i = 0,
            length = elems.length,
            isArray = isArraylike( elems ),
            ret = [];

        // Go through the array, translating each of the items to their new values
        if ( isArray ) {
            for ( ; i < length; i++ ) {
                value = callback( elems[ i ], i, arg );

                if ( value != null ) {
                    ret.push( value );
                }
            }

        // Go through every key on the object,
        } else {
            for ( i in elems ) {
                value = callback( elems[ i ], i, arg );

                if ( value != null ) {
                    ret.push( value );
                }
            }
        }

        // Flatten any nested arrays
        return concat.apply( [], ret );
    },

    // A global GUID counter for objects
    guid: 1,

    // Bind a function to a context, optionally partially applying any
    // arguments.
    proxy: function( fn, context ) {
        var tmp, args, proxy;

        if ( typeof context === "string" ) {
            tmp = fn[ context ];
            context = fn;
            fn = tmp;
        }

        // Quick check to determine if target is callable, in the spec
        // this throws a TypeError, but we will just return undefined.
        if ( !jQuery.isFunction( fn ) ) {
            return undefined;
        }

        // Simulated bind
        args = slice.call( arguments, 2 );
        proxy = function() {
            return fn.apply( context || this, args.concat( slice.call( arguments ) ) );
        };

        // Set the guid of unique handler to the same of original handler, so it can be removed
        proxy.guid = fn.guid = fn.guid || jQuery.guid++;

        return proxy;
    },

    now: Date.now,

    // jQuery.support is not used in Core but other projects attach their
    // properties to it so it needs to exist.
    support: support
});