字符串、数组函数、分支和循环

作业标题：0709作业
作业内容：

实例演示常用的字符串和数组函数(自选5个即可)。
2.实例演示分支与循环,将课堂上列支的所有场景全部演示一遍。

字符串和数组函数

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8" />
  <meta http-equiv="X-UA-Compatible" content="IE=edge" />
  <meta name="viewport" content="width=device-width, initial-scale=1.0" />
  <title>字符串方法</title>
</head>
<body>
  <script>
    //concat():字符串拼装
    str = "html" + ", css" + ", js";
    console.log(str);
    str = "html".concat(", css", ", js");
    console.log(str);
    //slice():从子串
    str = "Hello PHP.CN";
     //slice():从子串
    str = "Hello PHP.CN";
    str.slice(0, 5);
    //Hello
    //Hello
    //substr()
    res = str.substr(0, 5);
    console.log(res);
    res = str.substr(-6, 3);
    console.log(res);
    let arr = [];
    //push:在尾部添加
    console.log(arr.push("a", "c", "d"));
    console.log(arr);
    //pop()从尾部删除
    console.log(arr.pop());
    console.log(arr);
  </script>
</body>
</html>

分支与循环

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8" />
  <meta http-equiv="X-UA-Compatible" content="IE=edge" />
  <meta name="viewport" content="width=device-width, initial-scale=1.0" />
  <title>分支、循环</title>
  <!-- if elseif else,switch,三元运行? :,while, do while, for, for in对象  for of数组  -->
</head>
<body>
  <script>
    //单分支
    let score = 39;
    if (score >= 60) {
      console.log("及格");
    }
    //双分支
    score = 59;
    if (score >= 60) {
      console.log("及格");
    } else {
      console.log("不及格");
    }
    //多分支
    score = 100;
    if (score >= 60 && score <= 70) {
      console.log("及格");
    } else if (score >= 70 && score <= 90) {
      console.log("不错");
    } else if (score > 100 || score < 0) {
      console.log("非法字符");
    } else if (score >= 90 && score <= 100) {
      console.log("优秀");
    } else {
      console.log("不及格");
    }
    //简化多分支
    score = 50;
    switch (true) {
      case score >= 60 && score <= 70:
        console.log("及格");
        break;
      case score >= 70 && score <= 90:
        console.log("不错");
        break;
      case score > 100 || score < 0:
        console.log("非法字符");
        break;
      case score >= 90 && score <= 100:
        console.log("优秀");
        break;
      default:
        console.log("不及格");
    }
    //while循环
    arr = [1, 2, 3, 4, 5];
    let i = 0;
    while (i < arr.length) {
      console.log(arr[i]);
      i++;
    }
    //do while循环
    arr1 = [1, 2, 3, 4, 5];
    i = 0;
    do {
      console.log(arr1[i]);
      i++;
    } while (i < arr1.length);
    //for循环
    arr2 = [1, 2, 3, 4, 5];
    for (let a = 0; a < arr2.length; a++) {
      console.log(arr1[a]);
    }
    //循环对象
    const user = {
      id: 1,
      name: "admin",
      email: "admin@php.cn",
    };
    for (let key in user) {
      console.log(user[key]);
    }
    //循环数组
    let arr3 = [1, 2, 3, 4, 5, 6, 7, 8];
    for (let value of arr3) {
      console.log(value);
    }
  </script>
</body>
</html>

字符串、数组函数、分支和循环

字符串、数组函数、分支和循环

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