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--- notes:javascript_cheat_sheet [2026/07/22 03:54]
132.255.158.177 old revision restored (2026/06/27 04:30)
+++ notes:javascript_cheat_sheet [2026/07/24 15:24] (current)
47.79.200.137 old revision restored (2026/06/25 10:17)
@@ Line 8: / Line 8: @@
   * JavaScript is the most popular scripting language on the internet and works in all major browsers.
-  * It is a lightweight, interpreted language that is embedded into webpages to add interactivity.
+  * It is a lightweight, interpreted, object-oriented language that is embedded into webpages to add interactivity.
   * JavaScript can read and write HTML page elements, react to events, validate data, create cookies.
   * JavaScript was invented by Brendan Eich of Netscape but is now known officially as ECMAScript (current version is ECMA-262).
@@ Line 22: / Line 22: @@
     * In an external file called from either the head or the body e.g. <script src="abc.js"></script>
-==== Javascript Basic Syntax ====
+==== Basic Syntax ====
   * JavaScript is case-sensitive.
   * Statements may omit the final semi-colon but should not.
   * Blocks may be grouped together using curly braces { }.
-  * JavaScript uses java-style comments: // and /* */.
+  * JavaScript uses java-style comments: %%//%% and /* */.
-  *
+  * JavaScript variables are case-sensitive and must begin with a letter or underscore.
+  * Variables are automatically declared when first used but should be explicitly declared using e.g. var a = 5;
+  * JavaScript uses standard C/Java operators e.g. +-*/%, ++, +=, &&, ||, !, + (concatenation).
+  * JavaScript uses C/Java comparators >,>=,==, !=, a?b:c. It also uses === to test equality of value and type.
+==== Basic Structures ====
+  * if {} else if {} else {}
+  * for (var=start;var%%<=%%end;var=var+inc) {}
+  * while (condition) {}
+  * do {} while (condition) ;
+  * //break// and //continue// both valid in a loop.
+  * for (element in array) {}
+  * for (property in object) {}
+  * switch (n) { case 1: stmt; break; default: stmt; }
+  * function name(var1,var2,...) {}
+  * \", \n, \t, \r, \', \&, \\
+==== Events, Error Handling and Popups ====
+  *  try { throw "errname"; } catch(err) {}
+  * onerror=handleErr; handleErr(msg,url,linenum)
+  * if handleErr returns false, browser displays a standard error message in the JavaScript console.
+  * an alert box just has an OK button - alert("msg")
+  * a confirm box returns true if the user clicks OK, false if he clicks cancel - confirm("msg")
+  * a prompt box allows the user to enter a value. It returns true if the user clicks OK, false if he clicks cancel - prompt("msg","defaultvalue");
+  *  JavaScript functions can be registered to run on certain events (event="jscode" in an HTML element):
+    * onunload, onload (page or image), onresize, onabort
+    * onfocus, onblur, onclick, ondblclick
+    * onmouseover, onmouseout, onmousemove
+    * onchange, onsubmit, onreset, onselect
+    * onkeydown, onkeypress, onkeyup
+    * onmousedown, onmouseup
+==== JavaScript Objects ====
+  * Objects have properties and methods.
+  * String objects have a length property and methods including: indexOf, match, replace
+  * new Date() creates a Date object (with today's date).
+  * Date objects include methods: getTime(epoch), setFullYear, toUTCString, getDay, getHours
+  * Date objects can be compared using <, > .
+  * To declare an array <code javascript> var mycars=new Array("Saab","Volvo","BMW");</code>
+  * Arrays have methods including: sort, concat, join.
+  * To sort an integer array, must use a function <code javascript> function intSort (a, b){ return a - b;}</code>
+  * The Math object contains common math routines: round, random, e, pi etc.
+  * The RegExp object supports regexp creation and searching including methods: test (t/f), exec, compile (alter).
+  * HTML DOM objects allow access to browser and webpage.
+==== Advanced JavaScript ====
+  * navigator.appName/appVersion contain the browser name and version.
+  * document.cookie allows read and write access to cookie so to set a cookie <code javascript>
+function setCookie(c_name,value,expiredays)
+{
+  var exdate=new Date();
+  exdate.setDate(exdate.getDate()+expiredays);
+  document.cookie=c_name+ "=" +escape(value)+
+    ((expiredays==null) ? "" :
+     ";expires="+exdate.toGMTString());
+} </code>
+  * The onsubmit event can be used to validate a form.
+  * document.img_name.src ="pic.gif" changes an image.

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