jquery源码i为什么喜欢放外面

Question

例如这段，在其他很多地方也是，把i放在外面，而不是放在for里面

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;
    },

jquery源码这么写到底有啥好处

Answer 1

都一样，看个人风格

for(var i = 0; i < length; i++) {
    // 没区别...
}