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- // Javascript Cheat Sheet
- /************************************
- *********** DOM: How to... *********
- ************************************/
- // Find an element by its ID
- document.getElementById("anId");
- // Show an element
- element.show();
- // Hide an element (display:none;)
- element.hide();
- /************************************
- ************** Variables ************
- ************************************/
- // Variables: All data has a type associated with it which determines what you can do with it.
- "I'm a string" // string: a chain of characters
- 1 // number: integer
- 1.2 // number: float
- true // boolean: true or false
- ["I'm a string", 1, 1.2, true, false] // array: stores multiple values in a single variable
- // Set variables
- var string = "I'm a string";
- var integer = 1;
- var float = 1.2;
- var boolean = true;
- var array = ["I'm a string", 1, 1.2, true];
- // Change variables
- string = "I'm still a string but with another value";
- integer = 2;
- boolean = false;
- /************************************
- *********** Math expressions *********
- ************************************/
- + // Add
- - // Remove
- * // Multiply
- // Devide
- /
- % // Modulo: returns the remainder when a division is executed.
- 3 % 3 // Returns 0
- 3 % 2 // Returns 1
- ++ // Adds 1
- -- // Removes 1
- // Comparisons
- == // Equal
- != // Different
- > // Superior
- < // Inferior
- >= // Superior or equal
- <= // Inferior or equal
- // Conditions
- if (someCondition == true) {
- // do something
- }
- else if (someOtherCondition == false) {
- // do something
- }
- else {
- // do something
- }
- /************************************
- ************** Use Case 1 ***********
- ************************************/
- var recipe = "Porridge";
- var packets = 3;
- var isScottish = true; // camelCase when a variable is made of many words.
- var myBreakfast = "I like having " + recipe + " at breakfast. In fact I eat " + packets + " packets a week.";
- if (isScottish == true) {
- document.getElementById("breakfast").innerHTML = myBreakfast;
- }
- else {
- document.getElementById("breakfast").innerHTML = "I only have coffee.";
- }
- /************************************/
- /********* Objects: How to... *******/
- /************************************/
- // Get all properties of an object
- Object.getOwnPropertyNames(replaceWithYourVariable);
- /************************************/
- /*************** Loops **************/
- /************************************/
- // While loop
- var numbers = [1, 2, 3, 4, 10, 20];
- var incrementer = 0;
- while (incrementer < numbers.length) {
- numbers[incrementer] *= 2;
- incrementer ++;
- }
- // returns numbers = [2, 4, 6, 8, 20, 40]
- // For loop
- var numbers = [1, 2, 3, 4, 10, 20];
- for (var i = 0; i < numbers.length; i++) { // first we set the value of i, then we set the condition and at the end the incrementent.
- numbers[incrementer] *= 2;
- }
- // returns numbers = [2, 4, 6, 8, 20, 40]
- /************************************/
- /************* Functions ************/
- /************************************/
- function sandwich(filling) { // Define a new function. "filling" is an optional argument. Leave empty parenthesis if the argument is not needed.
- alert("A delicious " + filling + " sandwich!");
- }
- sandwich("extra butter"); // Then use it
- /************************************/
- /************** Events **************/
- /************************************/
- // Click event
- selector.onclick = function(){
- // Do something
- };
- // Hover event
- selector.onmouseover = function(){
- // Do something
- };
- /************************************/
- /******** Declare Javascript ********/
- /************************************/
- // Inline, in the HTML. NOT RECOMMENDED
- <button onclick="style.backgroundColor = 'yellow';">Click me!</button>
- // At the end of the <body>
- <script>
- document.getElementById("button").onclick = function(){
- this.style.backgroundColor = 'yellow';
- }
- </script>
- // In a separated file
- <head>
- <script type="text/javascript" src="url/to/source"></script>
- </head>
- /************************************/
- /************ Libraries *************/
- /************************************/
- // jQuery
- // Instead of innerHTML = something;
- $( "button.blue" ).html( "I'm feeling blue." ); // Use CSS selectors
- // Instead of onclick = function(){};
- $( "button.clickMe" ).click(function(){
- $(this).css("background-color", "blue");
- });
- // Instead of onmouseover
- $( "button.hoverMe" ).hover(function(){
- $(this).hide();
- });
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