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JavaScript - programming language for HTML
Number in the JavaScript | standard ES5
посмотрели
8457
раз
обновлено: 1 Augusta 2020
To declare a numeric variable, you need to write:
var Name = 25;
or
var Name = 34.7;
or
var Name = Number(30);
or
var Name = new Number(30);
Example
Html
<script>
// Option 1. Integer
var
value1 = 45;
// Option 2. Fractional number
var
value2 = 23.56;
// Option 3. Class Number contains an integer
var
value3 = Number(
"45"
);
// Option 4. The Number class contains an integer
var
value3 = new Number(
"45"
);
</script>
Conversion string → to a fractional number
Html
<script>
// Converts to number (if all characters are numbers or dots)
var
value = Number(
"56.2"
);
// value = 56.2
var
value = Number(
"56.2 a"
);
// value = NaN
// Converts to number (if not all digit characters are)
var
value = parseFloat(
"123.45 a"
);
// value = 123.45
var
value = parseFloat(
"Hello 123.45 a"
);
// value = NaN
</script>
Conversion error, check after conversion Number.isNaN(...)
Html
Example
<script>
var
value = parseFloat(
"Hello 123.45 a"
);
// value = Nan
var
isError = Number.isNaN(value);
// isError = true
</script>
Conversion string → to an integer
Html
<script>
// Converts to number (if all characters are digits)
var
value = Number(
"56"
);
// value = 56
var
value = Number(
"56 a"
);
// value = NaN
// Converts to number (if not all digit characters are)
var
value = parseInt(
"82 dfg"
);
// value = 82
var
value = parseInt(
"a 82 dfg"
);
// value = NaN
</script>
Convert hexadecimal number → to a decimal number
Html
<script>
var
value = parseInt(
"0x23"
, 16);
// 16 it is a sixth-supratice system
// value = 35
</script>
Round a fractional number with decimal precision. Function toFixed
Html
<script>
var
value = Number(
"123.497"
);
var
fix = value.toFixed(2);
// round a number to 2 decimal places
// fix = 123.50
var
value = Number(
"56.2347"
);
// round a number to 2 decimal places
var
fix = value.toFixed(2);
// fix = 56.23
</script>
The integer part of the number. Function Math.floor
Html
<script>
var
value = 123.97;
var
newValue = Math.floor(value);
// newValue = 123
var
value = 56.2347;
var
newValue = Math.floor(value);
// newValue = 56
</script>
Round a fractional number to an integer. Function Math.round
Html
<script>
var
value = 123.97;
var
newValue = Math.round(value);
// newValue = 124
var
value = 56.2347;
var
newValue = Math.round(value);
// newValue = 56
</script>
Round a fractional number to an integer. Function Math.ceil
Html
<script>
var
value = 123.97;
var
newValue = Math.ceil(value);
// newValue = 124
var
value = 56.001;
var
newValue = Math.ceil(value);
// newValue = 57
</script>
Number modulus (if the number negative becomes positive). Function Math.abs
Html
<script>
var
value = -123.97;
var
newValue = Math.abs(value);
// newValue = 123.97
var
value = 56.001;
var
newValue = Math.abs(value);
// newValue = 56.001
</script>
All Features Number
msdn.microsoft.com
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Mathematical functions from the library Math: Sin, cos, log, pow and so on in the JavaScript | standard ES5
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Объявления
Объявления
•
In which editor (program) is it convenient to write JavaScript code?
New app
•
Create a new application JavaScript in a text editor
•
Create a new application JavaScript in Visual Studio Code. Debug the application. See in debugging how to perform JavaScript
Debugging JavaScript, HTML
•
Debug JavaScript in Google Chrome. Using debugger
•
How to find out (see) where the error is when executing HTML, JavaScript in Google Chrome
•
Debugging JavaScript in the Google Chrome. Use console.log("Hello!")
JavaScript стандарт ES5. Издан в 2009 году. Поддерживается всеми браузерами
Function
•
Function in the JavaScript. Example: function CalculateSum(value1, value2) { ... } | standard ES5
•
Function return || in the JavaScript. Example: function getPersonName(name) { return name || "Evgen" } | standard ES5
•
Call a function before it is defined (Hoisting) in the JavaScript | standard ES5
•
Variables within a function (lifetime of variables within a function) JavaScript | standard ES5
•
Pass parameters by value and by reference to the function in the JavaScript | standard ES5
•
How to find out... whether there is a function by name in the JavaScript? Example: typeof calcSum == "function" | standard ES5
•
The function described inside the function. JavaScript | standard ES5
Unnamed function
•
Unnamed function in the JavaScript . Using an unnamed function: create a new variable and assign an unnamed function to a new variable. Example: var myFunc1 = function (a, b) { return a + b; } ; | standard ES5
•
Unnamed function in the JavaScript . Using an unnamed function: pass an unnamed function as a parameter to another function. Example: Calculate(15, 7, function(v1, v2) {return v1+v2;}); | standard ES5
Само-вызывающая безымянная функция
•
Self-calling unnamed function in the JavaScript. Where is it used? Used in Yandex advertising. Example: ( function(){ ... } )(); | standard ES5
•
Create a file js with an object containing export variables and functions. This is an example of using a self-calling unnamed function | standard ES5
Lambda function (abbreviated version of the unnamed function)
•
Lambda function in the JavaScript . Use the lambda function. [Example1] var myFunc1 = (a, b) => a + b; [Example2] Calculate(15, 7, (v1, v2) => {return v1+v2;}); | standard ES5
Variables
•
Variables in the JavaScript (text, number, flag, date and time) | standard ES5
•
Accessing Variables Before Defining Them (Hoisting) in the JavaScript | standard ES5
•
Variable scope var, let, const in the JavaScript | standard ES5
Text, strings in the JavaScript
•
Text in the JavaScript. Class String. Example: var myText = String("World"); | standard ES5
•
Length (string length in the JavaScript) | standard ES5
•
Function replace(text1, text2) replace text in the JavaScript | standard ES5
•
Function toUpperCase() converts text to uppercase JavaScript | standard ES5
•
Function toLowerCase() lowercase text JavaScript | standard ES5
•
Function split(delimiter) splits a string into substrings JavaScript | standard ES5
•
Function charAt(position) get a symbol by position JavaScript | standard ES5
•
Function substr(pos, len) returns a substring JavaScript | standard ES5
•
Function slice(pos1, pos2) returns a substring JavaScript | standard ES5
•
Function substring(pos1, pos2) returns a substring JavaScript | standard ES5
•
Function indexOf(text, startPos) searches for a substring and returns an index JavaScript | standard ES5
•
Function startsWith(text) Checks, whether the line begins with the specified substring JavaScript | standard ES5
•
Function trim() remove spaces at the beginning and end of a line JavaScript | standard ES5
•
Функция padStart(length, symbol) добавляет в начале строки символы до нужной длины строки JavaScript | стандарт ES5
•
Функция padEnd(length, symbol) добавляет в конце строки символы до нужной длины строки JavaScript | стандарт ES5
•
В текстовую переменную можно назначить текст как много строк. Пример: var myText = `Hello \n Thanks \n Bye` | JavaScript standard ES6
•
In a text variable, you can write expressions with variables (formatting, string interpolation). Example: var myText = `Hello ${a}` | JavaScript standard ES6
Регулярные выражения
•
Регулярные выражения в JavaScript | standard ES5
•
Write a regular expression to remove all special characters except letters and numbers | Regex JavaScript | standard ES5
Numbers and mathematical functions
•
Number in the JavaScript. Convert text to a number. Rounding a number. Convert hexadecimal to decimal. | standard ES5
•
Mathematical functions from the library Math: Sin, cos, log, pow and so on in the JavaScript | standard ES5
Date & Time
•
Date & Time (year, month, date, hours, minutes, seconds) in the JavaScript. Class Date | standard ES5
Array
•
Array in the JavaScript This is [] or class Array | standard ES5
•
Что значит 3 точки ...items | Пример 1: Math.max(...prices) | Пример 2: books.push(...items) | JavaScript, стандарт ES5
•
Difference between push(items) and push(...items) | Adding an Array to an Array in the JavaScript | standard ES5
•
Найти max цены в сложном массиве: [ {name:"Tomate", price:10}, {name:"Apple", price:17}, {name:"Orange", price:15} ] в JavaScript | стандарт ES5
•
Найти min цены в сложном массиве: [ {name:"Tomate", price:10}, {name:"Apple", price:17}, {name:"Orange", price:15} ] в JavaScript | стандарт ES5
Collection Map and Set
•
Collection "The key-meaning" in the JavaScript. Class Map | standard ES5
•
Collection of unique values in the JavaScript. Class Set | standard ES5
Object {set of properties and functions}
•
{} it's an object in the JavaScript. An object contains a set of properties and functions. Example var book = {Name: "Wizard of the Mediterranean", Price: 120}; | standard ES5
•
{...} = объект в JavaScript заполняем из переменных класса или другим объектом. Пример: const {name, total, price} = b.myProps; | standard ES5
Class (it is a function using new) | стандарт ES5
•
Class in the JavaScript this is a common constructor function. Such a constructor function contains simple data, objects, internal functions in the JavaScript. To create a class object, use new Example: function Book() { ... } ... var obj1 = new Book(); | стандарт ES5
•
Encapsulating variables (hiding variables for access) in the function (as a class) in the JavaScript | standard ES5
•
prototype - is a set of functions, variables for all instances of the class (as a function) in the JavaScript | standard ES5
try catch
•
Why you need to use try and catch in the JavaScript? | standard ES5
Closing (closure) in the Javascript
•
What are closures? (closure) in the JavaScript ? Standard ES5
Управление памятью в JavaScript
•
Управление памятью в JavaScript | standard ES5
Examples of picture movement and animation
•
Анимация человечка на месте. Используем HTML элемент <div>. Для анимации используем CSS стили: "animation", "background-image", "background-position", "keyframes" | standard ES5
•
Анимация человечка в движении (sprite). Используем HTML элементы <div>, <img>. Для анимации используем CSS стили: "animation", "background-image", "background-position", "keyframes" | standard ES5
•
Рисуем картинку с движением. Используем HTML элемент <canvas>. Для движения используем JavaScript: var img = new Image(), img.src = url, drawImage, timer, window.setInterval | standard ES5
•
Drawing a picture with movement and animation (sprite). Используем HTML элемент <canvas>. Для движения используем JavaScript: var img = new Image(), img.src = url, drawImage, timer, window.setInterval | standard ES5
Examples
•
Как определить устройство (планшет, компьютер, телефон) сейчас используется в JavaScript, HTML | standard ES5
•
Text Editor write in HTML, JavaScript | standard ES5
Do Popup using HTML and Javascript
•
How to make a Popup window in a HTML page | Javascript, HTML, CSS
Моя игра (HTML, JavaScript)
•
Моя игра "Wizard World" | HTML, JavaScript
PDF readers. Загрузка и отображение файла PDF (JavaScript, HTML)
•
PDF reader. Загрузка и отображение файла PDF (adobe JavaScript, HTML) | PDF JavaScript implemented by Adobe
•
PDF reader. Download and display a file PDF (JavaScript, HTML) | PDF JavaScript implemented by Mozilla
JavaScript стандарт ES6. Издан в 2015 году. Поддерживается НЕ всеми браузерами. Синонимы ES6, ES2015, ECMAScript 2015
•
In a text variable, you can write expressions with variables (formatting, string interpolation). Example: var myText = `Hello ${a}` | JavaScript standard ES6
•
class | Class in the JavaScript. Example: class Book {...} ... var obj1 = new Book(); | стандарт ES6
•
promise in the JavaScript | standard ES6
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