Javascript高级程序设计-第一阶段

/*//1、获取逻辑像素

var pageWidth = window.innerWidth;
var pageHeight = window.innerHeight;

console.log("pageWidth:" + pageWidth);
console.log("pageHeight:" + pageHeight);

if (typeof pageWidth != "number") {
    if (document.compaMode === "CSS1Compat") {

    }
}

//2、获取窗口位置
var leftPos = (typeof window.screenLeft == "number") ? window.screenLeft : window.screenX;

var topPos = (typeof window.screenTop == "number") ? window.screenTop : window.screenY;

console.log("position left:" + leftPos);
console.log("position top:" + topPos);

//2、 两个比较运算符的却别
console.log("===:" + (null === undefined)); //true
console.log("==:" + (null == undefined)); // false

3、 setTimeout() 应用
var date1 = new Date();

console.log(parseInt(date1.getTime()));

var date2 = new Date();

setTimeout("", 2000);

console.log(parseInt(date2.getTime()));

console.log(date1.getTime() - date2.getTime());

4、 clearTimeout(func, time) 应用

function demo() {
    var date = new Date();
    console.log(date);
}
var t = setInterval(demo, 500);

setTimeout("clearInterval(t)", 3000);

5、 定时器： 所有dom元素渲染完后才开始计时
setTimeout("alert(‘deefe‘)", 3000);

//5、闭包

function createFunction() {
    var result;

    for (var i = 0; i < 10; i++) {
        result[i] = function() {
            result[i].index = i;
            return i;
        }
    }
    console.log(result[0].index);
    return result;
}

function createFunction() {
    var result = new Array();

    for (var i = 0; i < 10; i++) {
        result[i] = function(num) {
            return function() {
                result[i].index = i;
                console.log(i);
                return num;
            };
        }(i);
    }

    return result;
}

console.log(createFunction());

//6、三目运算符
console.log((x > y ? x : y) > z ? (x > y ? x : y) : z);

//7、求最大值
Math.max() 不能传入数组， 只能传入参数列
console.log(max(12, 23, 1));

function max() {
    var arr = [12112, 21, 212, 12, 3213];
    return Math.max(arr);
}

//8、回调函数，返回上一步操作，每一次结果保存在内存中，占用内存
function factorial1(num) {
    if (num > 0) {
        return num * factorial1(num - 1);
    } else {
        return 1;
    }
}

//9、回调函数，讲结果返回，不占用多余的内存
function factorial2(num, total) {
    if (num > 0) {
        return total = num * factorial2(num - 1);
    } else {
        return 1;
    }
}

var n = 10;
console.log("factorial1(" + n + "):" + factorial1(n));
console.log("factorial2(" + n + "):" + factorial2(n));

//10、函数中断方式
function say() {
    console.log("1"); // 1
    return 0;
    console.log("2"); //函数已经结束没有执行
}

中断循环的方式
1.
break
2.
continue

//11、ECMScript 完整的解析器
alert(eval("1+2"));

//12、闰年判断
var j = 1;
for (var i = 1; i <= 3000; i++) {
    if (getYear(i)) {
        console.log(j + ":" + i);
        j++;
    }
}

function getYear(year) {
    if (year % 400 == 0 || (year % 4 === 0 && year % 100 != 0)) {
        return 1;
    } else {
        return 0;
    }
}

//13、push(),pop(),shift(),unshift()区别
var arr = [1, 2, 3];
arr.push(4);
console.log("push(4):" + arr); //1,2,3,4 从尾部添加

var arr = [1, 2, 3];
arr.pop(4);
console.log(arr); //1,2  从尾部出栈

var arr = [1, 2, 3];
arr.unshift(4)
console.log(arr); //4,1,2,3 从头部添加

var arr = [1, 2, 3];
arr.shift(4);
console.log(arr); // 2,3  从尾部添加

//14、++在前面和在后面的区别
var n = 100;
alert(++n); // 101
var m = 100;
alert(m++); //100

//15、条件操作符
console.log(12 > 4 ? "yes" : "no");

*/