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This blog is suitable for those who just come into contact with JS and want to review after a long time. This article is about “JavaScript functions”.

🌊🌈 About:

📚4.3_ Function synthesis case

📙4.3.1_ Use the function to find the maximum value of all parameters

function getMax(){
var max = arguments[0];

for(var i = 1; i < arguments.length; i++) {
if (arguments[i] > max) {
max = arguments[i]; }}return max;
}

console.log( getMax(1.2.3));// Output: 3
console.log( getMax(1.2.3.4.5));// Output: 5
console.log( getMax(11.2.34.Awesome!.5.100));// Output: 666
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📗4.3.2_ Use functions to reverse the array element order

function reverse(arr){
var newArr = [];
for(var i = arr.length - 1; i >= 0; i--){
newArr[newArr.length] = arr[i];
}
return newArr;
}
var arr1 = reverse( [1.3.4.6.9]);console.log(arr1);// output :(5)[9,6,4,3,1]
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📘4.3.3_ Using functions to judge leap years

function isLeapYear(year){
var flag = false;
if(year % 4= =0 && year % 100! =0 || year % 400= =0){
flag = true;
}
return flag;
}
console.log( isLeapYear(2020)?'2020 is a leap year ' : '2020 is not a leap year ' );// 2020 is a leap year
console.log( isLeapYear(2021)?'2021 is a leap year ' : '2021 is not a leap year ' );// 2021 is not a leap year
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📒4.3.4_ Gets the number of days in February for the specified year

// Add 4.3.3 code to the answer to this question
function fn(){
var year = prompt('Please enter a year');
if ( isLeapYear(year) ){
alert('The current month is a leap year. February has 29 days.')}else{
alert('The current month is a normal year. February has 28 days.')}}function isLeapYear(year){
var flag = false;
if(year % 4= =0 && year % 100! =0 || year % 400= =0){
flag = true;
}
return flag;
}

fn();
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📚4.4_ Function progression

📙4.4.1_ Function expressions

A function expression is an assignment of a declared function to a variable through which the function is called and the parameters are passed.

// Declare the function
function funcName() {
/ / the function body
}
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var sum = function (num1, num2) {
// Function expression
return num1 + num2;
};
console.log ( sum(1.2));/ / 3
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A function expression is defined in much the same way as a function declaration, except that a function expression must be defined before a call is made, whereas a function declaration does not limit the order in which it is declared and called. Since sum is a variable name and the function assigned to the variable has no function name, the function is also called anonymous.

The variable sum can be called as a function when an anonymous function is assigned to it.

📗4.4.2_ callback function

function cal(num1,num2,fn){
return fn(num1,num2);
}
console.log( cal(45.55.function(a,b){
returna+b; }));console.log(cal(10.20.function(a,b){
returna*b; }));Copy the code

📘4.4.3_ Recursive calls

A recursive call is a special call in a nested call to a function.

It refers to the process by which a function calls itself inside another function. This function becomes a recursive function.

The difference between a recursive function and a callback function, that’s what you need to think about

It is important to note that recursive functions can only be used in specific situations, such as computing factorials.

function factorial(n){  // Define the callback function
if( n == 1) {return 1;
}
return n * factorial(n - 1);
}
var n = prompt('Find n factorial \n. N is a positive integer greater than or equal to 1. For example, 2 means find 2! . ');
n = parseInt(n);
if(isNaN(n)){
console.log('N input is not valid');
}else{
console.log(n + The factorial of 'is :'+factorial(n));
}
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Oneself think of a way to do, for just learn small white, a little difficult

That’s the end of today’s introductory study

Peace

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Akken’s HTML, CSS guide for getting started (1)_HTML basics akken’s HTML, CSS guide for getting started (2)_HTML page elements and attributes Akken’s HTML, CSS guide for getting started (3)_ Text style attributes Aken’s HTML, CSS getting started guide (four)_CSS3 selector Aken’s HTML, CSS getting Started guide (five)_CSS box model Aken’s HTML, CSS getting Started guide (six)_CSS box model Aken’s HTML, CSS getting Started guide (seven)_CSS box model Akken’s HTML, CSS guide for getting started (eight)_CSS box model akken’s HTML, CSS guide for getting Started (nine)_ Floating and positioning Akken’s HTML, CSS guide for getting started (ten)_ Floating and positioning Akken’s HTML, CSS Guide for getting started (eleven)_ Floating and positioning Ken’s HTML, CSS guide for getting started (12)_ Form application of HTML, CSS guide for getting started (13)_ form application of HTML, CSS guide for getting started (14)_ Form application of HTML, CSS guide for getting started (15)_ Form application Ken o HTML, CSS, getting started guide (16) _ multimedia technology suggest collection 】 【 share | JS dry challenge the shortest time take you into the JS (a) suggest collection 】 【 share | JS dry challenge the shortest time take you into the JS (2) share | JS dry goods Recommended collection 】 challenge the shortest time take you into the JS (3) suggest collection 】 【 share | JS dry challenge the shortest time take you into the JS (4) suggest collection 】 【 share | JS dry challenge the shortest possible time to take you into the JS (5)

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