javascript String functions
// multiline string old school tip trick
// create elemnt div style none or hidden with text
var sMulitilineString = document.getElementById('idHiddenDiv').innerHTML; // get text from hidden div
// ES6 with quotes
const htmlString = 'Say hello to
multi-line
strings!';
(typeof "813") // string
(typeof 813) // number
parseInt("10.33") // returns 10 string to integer
parseInt('2def8'); // 2
parseInt('a2def8'); // NaN
parseFloat("10.33") // returns 10.33 string to float
var test_1 = 'string';
var test_2 = ' example';
var suma = test_1 + test_2;
var length = suma.length; // 14
var le = test_1.length; // 6
charAt(index)
/* Returns the character at the specified index */
var str = new String('Sample');
str.charAt(3)); // p
// startsWith
var str = "HELLO WORLD";
var res = str.charAt(0); // H
// endsWith
var res = str.charAt(str.length - 1); // D
charCodeAt(index)
/* Returns an integer representing the Unicode encoding
of the character at the specified location */
var str = new String('Sample');
str.charCodeAt(3)); // 112
fromCharCode([code1[, code2[, ...[, codeN]]]])
/* Returns a string from a number of Unicode character values */
var e = window.event;
var str = String.fromCharCode(e.keyCode); // keydown etc.
concat([item1[, item2[, . . . [, itemN]]]])
/* Returns a new array consisting of a combination of two or more arrays */
var arr1 = new Array("Hello, ", "Dolly uranove");
var arr2 = new Array("World!", "dort");
var myConcatArray = arr1.concat(arr2);
alert(myConcatArray[3]); // dort
concat([string2[, string3[, . . . [, stringN]]]])
/* Returns a string value containing the concatenation
of two or more supplied strings */
var string1 = new String("Hello, ");
var string2 = new String("World!");
var myConcatString = string1.concat(string2); // Hello, World!
indexOf(subString[, startIndex])
/* Returns the character position where the first occurrence
of a substring occurs within a String object */
lastIndexOf(substring[, startindex])
/* Returns the last occurrence of a substring within a String object */
localeCompare(stringExp)
/* Returns a value indicating whether two strings
are equivalent in the current locale */
var str1 = "1";
var str2 = "2";
var n = str1.localeCompare(str2); // -1
var str1 = "2";
var str2 = "2";
var n = str1.localeCompare(str2); // 0
var str1 = "a";
var str2 = "b";
var n = str1.localeCompare(str2); // -1
var str1 = "b";
var str2 = "a";
var n = str1.localeCompare(str2); // 1
match(rgExp)
/* Executes a search on a string using a regular expression
pattern, and returns an array containing the results of that search */
var rgExp = /some text/g;
replace(rgExp, replaceText)
/* Returns a copy of a string with text replaced
using a regular expression or search string */
search(rgExp)
/* Returns the position of the first substring
match in a regular expression search */
n // A newline character
. // Any character except a newline
r // A carriage return character
t // A tab character
b // A word boundary (the start or end of a word)
B // Anything but a word boundary
d // Any digit (same as [0-9])
D // Anything but a digit (same as [^0-9])
s // Single whitespace (space, tab, newline, etc.)
S // Single nonwhitespace
w // A "word character” (same as [A-Za-z0-9_])
W // A "nonword character” (same as [^A-Za-z0-9_])
slice(start, [end])
/* Returns a section of an array or string */
var myString = new String("This is a test");
var mySlice = myString.slice(2,6); // is i // pos: 2 to 5 // 0==T, 1==h, 2==i, 3==s, 4==" ", 5==i
mySlice = myString.slice(-3); // est // end of string
mySlice = myString.slice(0); // This is a test
split([separator[, limit]])
/* Returns the array of strings that results
when a string is separated into substrings */
var str = "one two three";
var words = str.split(" ");
var len = words.length; // 3
substring(start, end)
/* Returns the substring at the specified location
within a String object */
var inpTxt = "Hello there";
alert(inpTxt.substring(6, 10)); // ther
substr(start [, length ])
// Returns a substring beginning at a specified
// location and having a specified length
var s = "The love in Spain.";
ss = s.substr(12, 5); // Spain
tolocaleLowerCase()
/* Returns a string where all alphabetic characters
have been converted to lowercase, taking into account
the host environment's current locale */
toUpperCase()
/* Returns a string where all alphabetic characters
have been converted to uppercase */
var myString = "My text";
myString.anchor //places an HTML anchor with a NAME attribute around specified text in the object
myString.big
myString.blink
myString.bold
myString.concat
myString.fixed
myString.fontcolor
myString.fontsize
myString.charAt
myString.charCodeAt
myString.indexOf
myString.italics
myString.lastindexOf
myString.length
myString.link
myString.match
myString.replace
myString.search
myString.slice
myString.small
myString.split
myString.strike
myString.sub //places HTML SUB tags around text in a String object
myString.substr
myString.substring
myString.sup
myString.toLowerCase
myString.toString
myString.toUpperCase
myString.valueOf
var str = "58";
var res = str.valueOf();
var type = (typeof res); // string
var str = 58;
var res = str.valueOf();
var type = (typeof res); // number
77LW NO topic_id
AD
Další témata ....(Topics)
Ukázky zaokrouhlení čísla v JavaScript.
var num = 123.45678;
var rounded = Math.round(num); // out: 123
var num = 123.5269;
var rounded = Math.round(num); // out: 124
var num = -3.5269;
var rounded = Math.round(num); // out: -4
var num = 3.5269;
var rounded = Math.round(num * 100)/100; // out: 3.52
var num = 3.5269;
var rounded = Math.round(num * 1000)/1000; // out: 3.526
var num = 3.5269;
var rounded = num.toFixed(3); // out: 3.527
c:xampphtdocs
Getter a Setter
Získej nebo Nastav.
Michal už není Váš kamarád, tak jej změníte pomocí set:
Získej nebo Nastav.
Třídy v javascript dovolují použití get a set instrukci.
get vrátí hodnotu určité zadané proměnné.
set jí může změnit.
class Person {
constructor(name) {
this.personName = name;
}
get pname() {
return this.personName;
}
// i kdyz set vypada jako funkce, musi mit pouze jeden parametr
set pname(x) {
this.personName = x;
}
}
var myFriend = new Person("Michael");
Jméno osoby přítele získáme například:
var strMyFriendName = myFriend.pname; // bez () na konci!!!!!!
alert(strMyFriendName);
Michal už není Váš kamarád, tak jej změníte pomocí set:
// hodnota se nepřirazuje do závorek (), ale pomocí = rovná se!!!!
myFriend.pname = "Renata";
strMyFriendName = myFriend.pname;
alert(strMyFriendName);
// IF variable is not defined (or has a falsey value) THEN set it to an empty object.
// ELSE do nothing (technically speaking, variable gets assigned to itself)
var variable = variable || {} ;
function test(){
console.log(1);
}
// when called
test(); // 1
// or
var a = test;
a(); // 1
// or autocall if code executed
var test2 = function(){
console.log(2);
}
// test2 is undefined because the function test2 has no return value
// return string
function stringTest(param) {
return 'Hello ' + ' ' + param;
}
console.log(stringTest("Alice")); // Hello Alice
// return number
function numberTest(param) {
return 6 + param;
}
console.log(numberTest(5)); // 11
// or autocall if code executed
// function is like other variables
// parenthesis is for made groups or call functions.
// Immediately-Invoked Function Expression,
// or IIFE for short. It executes immediately after it’s created.
(function(){
// all your code here
var foo = function() {};
window.onload = foo;
// ...
})();
// foo is unreachable here (it’s undefined)
//////////////////////////////
// IIFE Immediately Invoked Funtion Expression
var greeting = function(name) {
return 'Hello ' + ' ' + name;
}('John');
console.log(greeting); // Hello John
console.log(typeof greeting); // string
console.log(greeting('Suzan')); // Uncaught TypeError: greeting is not a function
///////////////////////
var val = (function(){
var a = 0; // in the scope of this function
return function(x){
a += x;
return a;
};
})();
alert(val(10)); //10
alert(val(11)); //21
///////////////////////
// create the structure
var testHash = {
a : 1,
b : function(){
console.log(4);
},
c: function(param){
var num = param +5;
return num;
}
}
console.log(testHash.a); // 1
testHash.b(); // 4
testHash['b'](); // 4
testHash.c(7); // 12
/////////////////////////
// or function like class
function TestClass(n) {
this.some_property = n;
this.some_method = function() {
console.log(this.some_property);
};
}
var foo = new TestClass(3);
var bar = new TestClass(4);
foo.some_method(); // 3
bar.some_property += 2;
bar.some_method(); // 6
// console.log(some_property); // Uncaught ReferenceError: some_property is not defined
//////////////////////////
function Car(brand, year) {
return {
brand: brand,
year: year
}
}
var honda = Car("Honda", 1999);
console.log(honda.brand); // Honda
console.log(honda.year); // 1999
honda.brand = "Honda new Generation";
honda.year = 2021;
console.log(honda.brand); // Honda new Generation
console.log(honda.year); // 2021
var mazda = Car("Mazda",1987);
console.log(honda.brand); // Honda new Generation
console.log(mazda.brand); // Mazda
//////////////////////////////////////
// simplified code
var TEST_CLASS = TEST_CLASS || {};
TEST_CLASS.pokus = TEST_CLASS.pokus || (function() {
// -------------------------------------------------------------------------
// Private static variables and methods
// -------------------------------------------------------------------------
var privateStaticNumber = 5;
var privateStaticString = "My privateStaticString: ";
var privateStaticArray = [];
function privateStaticMethod(){
console.log('privateStaticMethod');
}
// CONSTRUCTOR CTOR
return function(config) {
// ----- private variables -----
var me = this,
isPaused = false;
this.privateStaticNumber = config.firstParam;
this.privateStaticString = privateStaticString + config.secondParam; // += produce: undefined I am from secondParam
this.privateStaticArray = config.thirtParam;
// ----- private methods -----
function getMode (mode, speed) {
// document.getElementById(mode).addEventListener('click', function () { snakeSpeed = speed; });
}
// ----- public variables -----
me.correct = 0;
me.wrong = 0;
// ----- public methods -----
me.setString = function(val) {
this.privateStaticString = val;
};
me.getString = function() {
return this.privateStaticString;
};
me.publicMethod = function(param){
console.log(param + ' from me.publicMethod()');
};
}; // end CTOR
})();
// end TEST_CLASS.pokus
var _me = _me || {};
var _me_test = new TEST_CLASS.pokus({firstParam:8, secondParam:" I am from secondParam", thirtParam:[1,3,9]});
// TEST_CLASS.pokus.privateStaticMethod(); // is not a function
// TEST_CLASS.pokus.publicMethod("Hola!"); // TEST_CLASS.pokus.publicMethod is not a function
// TEST_CLASS.publicMethod("Hola hej!"); // TEST_CLASS.publicMethod is not a function
// TEST_CLASS.pokus.publicMethod(" Hello!"); // is not a function
_me_test.publicMethod(" Hello!"); // Hello! from me.publicMethod()
console.log( _me_test.getString()); // My privateStaticString: I am from secondParam
console.log( _me_test.isPaused); // undefined
Date: 04.11.2020 - 23:14
(function () {
String.prototype.isString = true;
String.prototype.trim = function () { return this.replace(/(^\s*)|(\s*$)/g, "") };
String.prototype.endsWith = function (a) { return this.substr(this.length - a.length) == a };
String.prototype.startsWith = function (a) { return this.substr(0, a.length) == a };
})();
Odkazy na online regex editory:
https://regex101.com/
https://www.debuggex.com/r/LyIpMYTAhJ9Gja4x
https://regex101.com/
https://www.debuggex.com/r/LyIpMYTAhJ9Gja4x
Editace: 8.2.2021 - 22:24
Počet článků v kategorii: 77
Url:javascript-string-functions