walkDOM

function walkTheDOM(node, func) {

    func(node);

    node = node.firstChild;

    while (node) {

        walkTheDOM(node, func);

        node = node.nextSibling;

    }

} 

getElementsByClassName

function getElementsByClassName(className) {

    var results = [];

    walkTheDOM(document.body, function (node) {

        var a, c = node.className, i;

        if (c) {

            a = c.split(' ');

            for (i = 0; i < a.length; i += 1) {

                if (a[i] === className) {

                    results.push(node);

                    break;

                }

            }

        }

    });

    return results;

} 

第六章

6.5 判断是不是数组

var is array = function (value) {

    return value &&

    typeof value.splice === 'function' &&

    typeof value.length=== 'number' &&

    typeof value === 'object' &&

    ! (value.propertyIsEnumerable ('length'));

};

写一个Reduce

Array. method ('reduce', function(f,value) {

var i;

for （i=0;i<this.length; i +=1) {

  value = f(this [i], value);

}

return value;

})

第七章 正则表达式

7.1 匹配url的正则

var parse_url =/^ (?: ([A-Za-z]+) :)? (\/{0,3}) ( [0-9.\-A-Za-z]+)(?:: (d+))? (?:\/([^?#]*))?(?:\? ([^#]*))? (?:#(.*))?$/;

var url ="http://www.ora.com: 80/goodparts?q#fragment";

匹配数字的reg

var parse_number =/^-?\d+(?:\.\d*)? (?:e [+\-]?\dt)?S/i;

var test= function (num) {

document.writeln(parse number.test (num) );

};

true test ("1");

false test ('number');

true  test('98.6");

false  test ('132.21.86.100');

true  test ('123.45E-67');

false  test ('123.45D-67');