07-javascript common built-in objects

JavaScript common built-in objects 1. How array Array1.1 arrays are created

// create an array directly var colors = [' Red ', ' blue ', ' green 'typeof(colors)); // using constructors to create arrays with the New keyword var New Array (); Console.log (Colors2,typeof(colors2));

1.2 Assigning values to arrays

var arr = []; // The subscript of the JS array is incremented from 0, starting with Python. // add elements to the array arr[0] = ' x'; arr[1] = 3; arr[3] = [1, 2, 3];console.log (arr); // iterating through an array, printing an element  for inch arr) {    console.log (arr[i]);}

1.3 Common methods of arrays

1-Merging of arrays concat ()

// 1-Merging of arrays concat () var f1 = [' Apple ', ' banana ']; var f2 = [' orange ', ' pear ']; var fruits = f1.concat (f2); Console.log (fruits);

2- Join () joins the elements in the array using the specified string, which forms a new string

// 2-join () joins the elements in the array using the specified string, which forms a new string var fruits = ["apple", "banana", "orange", "Pear"];console.log (Fruits.join (' * * * '));

3-Convert Array to string toString ()

// 3-Convert array to String toString () var fruits = ["apple", "banana", "orange", "Pear"];console.log (Fruits.tostring ());

4-slice (Start,end); Returns a section of an array, left-closed, right-open

// 4-slice (start,end); Returns the paragraph of an array, left-closed (Gu Tou regardless of tail) var fruits = ["apple", "banana", "orange", "Pear"];console.log (Fruits.slice (2,3));

5-pop to move the last element of the divisor group

// 5-pop to move the last element of the divisor group var fruits = ["apple", "banana", "orange", "Pear"];fruits.pop (); Console.log (fruits);

6-push () Adds an element to the array at the end

// 6-push () adds an element to the array at the end of the var fruits = ["apple", "banana", "orange", "Pear"];fruits.push (' grape '); Console.log (fruits) ;

7-reverse () flipping an array

// 7-reverse () flipping an array var fruits = ["apple", "banana", "orange", "Pear"];console.log (Fruits.reverse ());

8-sort sorting an array of arrays

// 8-sort sorting an array of arrays var fruits = ["apple", "pear", "banana", "Orange"];fruits.sort (); Console.log (fruits);

9-Determine if an array: IsArray ()

// 9-Determine if an array: IsArray () var fruits = ["apple", "pear", "banana", "Orange"];console.log (Array.isarray (fruits));

2. String String2.1 string Common methods

2.2 Common Method Demos

1-chartat () returns the character of the position of the specified index, starting at 0 increments

// 1-chartat () character that returns the position of the specified index var str = ' I love to eat fish. '; Console.log (Str.charat (0)); Console.log (Str.charat (1)); Console.log (Str.charat (2) );
Console.log (Str.charat (3)), Console.log (Str.charat (4)), Console.log (Str.charat (5));

2-concat returns a String value that represents the concatenation of two or more strings

// 2-concat Returns a String value that represents the concatenation of two or more strings var str1 = ' ban ', str2 = ' ana '; Console.log (Str1.concat (str2));

3-replace (b) replaces string A with string b

// 3-replace (b) replaces string A with string B var str = ' I love to eat fish. ' ; Console.log (str.replace (' fish ', ' meat '));

4-indexof () looks for the subscript of a character, and returns 1 if it finds the index of the first occurrence of the returned string. Same as Seach () method usage

// 4-indexof () finds the subscript of a character and returns 1 if it finds a subscript for the returned string. As with Seach () method usage var str = ' I love to eat fish. ' ; Console.log (Str.indexof (' I ')), Console.log (Str.indexof (' o ')); Console.log (Str.indexof ( ' W '));

5-slice (Start,end) left close right open (Gu Tou disregard tail) split string

// 5-slice (start,end) left closed right open split string var str = ' I love to eat fish. ' ; Console.log (Str.slice (2,6));

6-split (' A ', 1) splits the string with string A and returns a new array. If the second argument is not written, the entire array is returned, and if the number is defined, the maximum length of the array is returned

// 6-split (' A ', 1) splits the string with string A and returns a new array. If the second argument is not written, it returns the entire array, and if the number is defined, the maximum length of the array is returned var str = ' I love to eat fish. '  = Str.split ("); Console.log (' arr1 '= Str.split (', 2); Console.log (' arr2 ', ARR2);

7-substr (start,end) left closed right open

// 7-substr (statr,end) left closed right open var str = ' I love to eat fish. ' ; Console.log (Str.substr (0,7));

8-tolowercase () Turn lowercase

// 8-tolowercase () Turn lowercase var str = ' I love to eat fish. ' ; Console.log (' str: ', str); Console.log (' lower: ', str.tolowercase ());

9-touppercase () Turn capital

// 9-touppercase () turn capital var str = ' I love to eat fish. ' ; Console.log (' str: ', str); Console.log (' Upper: ', Str.touppercase ());

10-Convert Number type to string type

// 10-Convert number type to String type var num = 1314.1314; Console.log (num.tostring (),typeof(Num.tostring ())); // rounded Console.log (num.tofixed (),typeof(Num.tofixed ()));

3. Creation of date objects Date3.1 date objects

Create Date object only constructor one way, use the New keyword

// a Date object was created var New Date ();

3.2 Common methods for date objects

//Create a Date objectvarMyDate =NewDate ();//Get Date (1-31)Console.log (' GetDate (): ', Mydate.getdate ());//Get Month (0-11)Console.log (' GetMonth (): ', Mydate.getmonth ());//get four-bit yearsConsole.log (' getFullYear (): ', Mydate.getfullyear ());//get the day of the Week (0-6)Console.log (' GetDay (): ', Mydate.getday ());//Get Hours (0-23)Console.log (' GetHours (): ', Mydate.gethours ());//Get minutes (0-59)Console.log (' getminutes (): ', Mydate.getminutes ());//gets the number of seconds (0-59)Console.log (' getseconds (): ', Mydate.getseconds ());

4. Built-in object Math4.1math common methods

4.2Math Common Methods Demo

1-math.floor () Down rounding, ' floor function '

// 1-math.floor () down rounding, ' floor function ' var x = 1314.1314; var y = math.floor (x); Console.log (y);

2-math.ceil () rounding up, ' ceiling function '

// 2-math.ceil () rounding up, ' ceiling function ' var x = 1314.1314; var y = math.ceil (x); Console.log (y);

3-Calculate the maximum and minimum values for two numbers

// 3-Calculate the maximum and minimum values for two numbers var x = N, y =console.log (' min: ', Math.min (x, y)), Console.log (' Max: ', Math.max (x, y)) ;

4-Random number Math.random ()

// 4-Random number math.random () var rannum = math.random (); Console.log (rannum); [ Random number between 0,1]//  Min-max: Min+math.random () * (max-min)//  100-200 random number Console.log (100+rannum* (200-100));

07-javascript common built-in objects