java script

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java script是什么？让我们一起来了解一下吧！

java script是一种客户端脚本语言。它是作用在客户端浏览器里，并且不需要编译，可以很快的被浏览器自带的解析引擎运行。

java script有以下特点：

1. 语法与c、java相似，可以用任意文字编辑工具

2. 由浏览器的解析引擎运行

3. 以对象为基础

4. 是一种弱类型语言

java script有六种数据类型：string、boolean、null、number、undefined、object。

实战举例，具体步骤如下：

let big = document.querySelector('.big');        let small = document.querySelector('.small');        let NS = document.querySelector('.l');        let WE = document.querySelector('.r');        let box = document.querySelector('.box');        let Box = document.querySelector('.Box');          // 倒计时模块        var longNum = 10;        var shortNum = 3;        big.addEventListener('click', function () {            let inputNum = prompt('请输入你想设置的秒数:');            longNum = inputNum == '' ? longNum : inputNum;        })        small.addEventListener('click', function () {            let inputNum = prompt('请输入你想设置的秒数:');            shortNum = inputNum == '' ? longNum : inputNum;        })        green();        Green = setInterval(green, 1000);         function green() {            NS.children[2].className = 'green_s';            point(Box);            NS.children[2].innerHTML = longNum;            WE.children[0].className = 'red_s';            caveat(box);            WE.children[0].innerHTML = longNum;            if (longNum == -1) {                clearInterval(Green);                NS.children[2].className = 'green_end';                del(Box);                NS.children[2].innerHTML = '';                WE.children[0].className = 'red_end';                del(box);                WE.children[0].innerHTML = '';                longNum = 10;                NS.children[1].className = 'yellow_s';                WE.children[1].className = 'yellow_s';                yellow();                Yellow = setInterval(yellow, 1000);                remind(box);                remind(Box);            }            longNum--;        }         function yellow() {            NS.children[1].innerHTML = shortNum;            WE.children[1].innerHTML = shortNum;            if (shortNum == -1) {                del(box);                del(Box);                clearInterval(Yellow);                NS.children[1].className = 'yellow_end';                NS.children[1].innerHTML = '';                WE.children[1].className = 'yellow_end';                WE.children[1].innerHTML = '';                shortNum = 3;                NS.children[0].className = 'red_s';                caveat(Box);                WE.children[2].className = 'green_s';                point(box);                red();                Red = setInterval(red, 1000);            }            shortNum--;        }         function red() {            NS.children[0].innerHTML = longNum;            WE.children[2].innerHTML = longNum;            if (longNum == -1) {                clearInterval(Red);                NS.children[0].className = 'red_end';                del(Box);                NS.children[0].innerHTML = '';                WE.children[2].className = 'green_end';                del(box);                WE.children[2].innerHTML = '';                longNum = 10;                NS.children[2].className = 'green_s';                WE.children[2].className = 'green_end';                green();                Green = setInterval(green, 1000);            }            longNum--;        }         function caveat(concent) {            concent.style.color = 'red';            concent.innerHTML = '闯红灯,等着大家都去你家吃席';        }         function remind(concent) {            concent.style.color = 'yellow';            concent.innerHTML = '黄灯了,还没过去的抓紧时间,马上车就来撞你了';        }         function point(concent) {            concent.style.color = 'green';            concent.innerHTML = '绿灯也要注意安全哟!';        }         function del(concent) {            concent.innerHTML = '';        }