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创建一个包含1~100的数组.

var array = [];
for (var i = 1; i <= 100; i++) {
  array.push(i);
}
console.log(array);

定义一个数组，遍历输出它的每一项.

var array = [55, 45, 77, 88, 99, 101, 120];
for (var i = 0; i < array.length; i++) {
 console.log(array[i]);
}

输出1-100的所有奇数.

for (var i = 1; i < 100; i++) {
 if (i % 2 !== 0) {
  console.log(i);
 }
}

定义一个数组，输出数组中所有的奇数.

var array = [44, 55, 23, 45, 77, 88];
for (var i = 0; i < array.length; i++) {
 if (array[i] % 2 !== 0) {
  console.log(array[i]);
 }
}

定义一个数组，找出所有的奇数，放入到一个新数组中.

var array1 = [44, 55, 23, 45, 77, 8];
var array2 = [];
for (var i = 0; i < array1.length; i++) {
 if (array1[i] % 2 !== 0) {
  array2.push(array1[i]);
 }
}
console.log(array2);

1~100求和.

var sum = 0;
for (var i = 1; i <= 100; i++) {
 sum += i;
}
console.log(sum);

求某个数的阶乘.

function factorial(n) {
 var result = 1;
 if (n < 1) {
  return 0;
 }
 for (var i = 1; i <= n; i++) {
  result *= i;
 }
 return result;
}
console.log(factorial(5));

数组求和.

sum = 0;
var array = [1, 2, 3, 4, 5];
for (var i = 0; i <= array.length; i++) {
 sum += i;
}
console.log(sum);

求数组中的奇数的个数.

var count = 0;
var array = [1, 2, 3, 4, 6];
for (var i = 0; i < array.length; i++) {
 if (array[i] % 2 !== 0) {
  count++;
 }
}
console.log(count);

求数组中的奇数和.

var sum = 0;
var array = [1, 2, 3, 4, 7];
for (var i = 0; i < array.length; i++) {
 if (array[i] % 2 !== 0) {
  sum = sum + array[i];
 }
}
console.log(sum);

数组中是否存在某个数，输出 是 或 否.

var array = [77, 88, 66, 54, 32, 21, 1];
var target = 1;
var isFind = false;
for (var i = 0; i < array.length; i++) {
 if (array[i] === target) {
  isFind = true;
  break;
 }
}
if ((isFind = true)) {
 console.log("是");
} else {
 console.log("否");
}

数组中是否存在某个数，如果存在，则输出它所在的下标，如果不存在，则输出-1.

var array = [99, 55, 34, 25, 77, 65, 32];
var target = 65;
var index = -1;
for (var i = 0; i < array.length; i++) {
 if (array[i] === target) {
  index = i;
  break;
 }
}
console.log(index);
var array = [1, 2, 3, 477, 54, 88, 65];
for (var i = 0; i < array.length; i++) {
 console.log(i);
}

找到数组中第一个奇数和最后一个奇数，将它们求和.

var array = [55, 44, 65, 1, 2, 7, 15];
var sum = 0;
var isFind = false;
for (var i = 0; i < array.length; i++) {
 if (array[i] % 2 !== 0) {
  isFind = array[i];
 }
}
var last = false;
for (var i = array.length - 1; i >= 0; i--) {
 if (array[i] % 2 !== 0) {
  last = array[i];
 }
 sum = isFind + last;
}
console.log(isFind, last, sum);

有两个数组，看两个数组中是否都存在奇数，输出 是 或 否.

var array1 = [4, 44, 7, 10, 8, 22, 12];
var array2 = [22, 80, 22, 31];
var isFind1 = false;
var isFind2 = false;
for (var i = 0; i < array1.length; i++) {
 if (array1[i] % 2 !== 0) {
  isFind1 = array1[i];
  break;
 }
}
for (var i = 0; i < array2.length; i++) {
 if (array2[i] % 2 !== 0) {
  isFind2 = array2[i];
  break;
 }
}
if (isFind1 && isFind2) {
 console.log("是");
} else {
 console.log("否");
}

输出一个对象的所有键值对.

var obj = {
 a: 23,
 c: "jk",
 p: "75",
};
for (var key in obj) {
 console.log(key + "=" + obj[key]);
}

计算对象中字符串属性的数量.

var obj = {
 a: "55",
 jk: "45",
 oppo: "54",
 txp: 5,
};
var count = 0;
for (var key in obj) {
 if (typeof obj[key] === "string") {
  count++;
 }
}
console.log(count);

将一个对象所有的数字属性，转换为字符串，并在其前面加上￥.

var obj = {
 name: "xxx",
 balance: 199.8,
 taken: 3000,
};
var newobj = {};
for (var key in obj) {
 var velue = obj[key];
 if (typeof velue === "number") {
  newobj[key] = "￥" + velue;
 } else {
  newobj[key] = velue;
 }
}
console.log(obj, newobj);