Dynamic web pages with JavaScript

JS Intro Paragraph

prototype-based, multi-paradigm, single-threaded, dynamic language, supporting object-oriented, imperative, and declarative

JavaScript is NOT Java

scripting language that enables you to create dynamically updating content, control multimedia, animate image

const para = document.querySelector(‘p’);

para.addEventListener(‘click’, updateName);

function updateName() { const name = prompt(‘Enter a new name’); para.textContent = Player 1: ${name}; }

• this creates the ability to give a name in set box

Input and Output in JS

examples/js/pure_js_greating.html

First name: Last name:

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With a button,a div element, two input elements and each one with its own ID

Variables

4 Ways to Declare a JavaScript Variable:

• Using var
• Using let
• Using const
• Using nothing

Variables store values, like in algebra:

let x = 5; let y = 6; let z = x + y;

Use var when code is 1995 to 2015

Use let and const post 2015

const is the go to unless chnaging value of variable

const price1 = 5; const price2 = 6; let total = price1 + price2;

Identify variables with unique names, a must; case sensitive.

• Names can contain letters, digits, underscores, and dollar signs.
• Names must begin with a letter
• Names can also begin with $ and _ (but we will not use it in this tutorial)
• Names are case sensitive (y and Y are different variables)

• Reserved words (like JavaScript keywords) cannot be used as names

• = is the assignment operator*

• == is teh equal to operator*

• Declare variable with var or let then assign value*

Declare variables at begginnig of script

seperate variables with ,

• let person = “John Doe”, carName = “Volvo”, price = 200;

Re-declare variable, lose value!

• var carName = “Volvo”; var carName;

You can use = and +

• let x = 5 + 2 + 3;

$ and _ treat as variables