Table of contents
Exercises: 1: Create a function that calculates the sum of two numbers.
2: Encapsulate a function of the difference between two numbers.
3: Create a function that calculates the maximum of two numbers.
4: Create a function that passes an array and returns the maximum, minimum, and sum in the array.
5: Pass an array to realize the function of flipping the array.
6: Encapsulate a function: the browser receives a month to judge the number of days in the month.
8: Encapsulate a function to determine whether a certain value exists in an array.
Function definition:
Function: It is **encapsulating a code block that can be called repeatedly**. This code block can **reuse a large amount of code**.
Exercises:
1: Create a function that calculates the sum of two numbers.
function sum(num1, num2) {
return num1 + num2;
}
var sum = sum(1, 2);
console.log(sum); 2: Encapsulate a function of the difference between two numbers.
function getDiff(num1, num2) {
return num1 - num2;
}
ver diff = getDiff(1, 2);
console.log(diff); 3: Create a function that calculates the maximum of two numbers.
function getMax(num1, num2) {
if (num1 > num2) {
return num1;
} else {
return num2;
}
return num1 > num2 ? num1 : num2;
}
console.log(getMax(80, 55));
4: Create a function that passes an array and returns the maximum, minimum, and sum in the array.
var numArr = [10, 3, 11, 2, 20];
function getValue(arr) {
var numArr = [];
var max = arr[0];
var min = arr[0];
var sum = 0;
for (var i = 0; i < arr.length; i++) {
if (max < arr[i]) {
max = arr[i];
}
if (max < arr[i]) {
min = arr[i];
}
sum += arr[i];
}
numArr[0] = max;
numArr[1] = min;
numArr[2] = sum;
return numArr;
}
var newarr = getValue(numArr);
console.log(max + min + sum)5: Pass an array to realize the function of flipping the array.
function reverse(arr) {
var newarr = [];
for (var i = arr.length - 1; i >= 0; i--) {
newarr[newarr.length] = arr[i];
}
return newarr
}
var re = reverse([1, 2, 3, 4, 5, 6])
console.log(re); 6: Encapsulate a function: the browser receives a month to judge the number of days in the month.
function newday() {
var month = prompt("请输入月份：");
var day;
switch (Number(month)) {
case 1:
day = 31;
break;
case 2:
day = 28;
break;
case 3:
day = 31;
break;
case 4:
day = 30;
break;
case 5:
day = 31;
break;
case 6:
day = 30;
break;
case 7:
day = 31;
break;
case 8:
day = 31;
break;
case 9:
day = 30;
break;
case 10:
day = 31;
break;
case 11:
day = 30;
break;
case 12:
day = 31;
break;
default:
console.log("输入错误");
}
return day;
}
var day = newday();
console.log('这个月有' + day + '天');7: Make a simple calculator, the browser receives +,-*/, receives two numbers, and then calculates the result.
function getSum() {
var first = Number(prompt("请输入第一个数字："));
var symbol = prompt("请输入运算符：");
var second = Number(prompt("请输入第二个数："));
var res;
if (symbol == "+") {
res = first + second;
}
if (symbol == "-") {
res = first - second;
}
if (symbol == "*") {
res = first * second;
}
if (symbol == "/") {
res = first / second;
}
return res;
}
var res = getSum();
console.log(res);
8: Encapsulate a function to determine whether a certain value exists in an array.
var arr = [1, 10, 78, 90, 67]; //定义一个数组
function findItem(item, arr) { //封装一个函数
var flag = false; //默认这个数不在数据里面
//业务逻辑
for (var i = 0; i < arr.length; i++) {
if (item == arr[i]) { //如果找到了这个数
flag = true;
}
}
return flag;
}
//调用函数
var flag = findItem(1, arr);
console.log(flag);