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This is a summarized form of the JavaScript Tutorial.

For reference JavaScript specifications can be found here .

• 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.
• 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).
• A simple “Hello World” example

  <script type="text/javascript">
  <!--
  document.write("Hello World!");
  //-->
  </script> 

• JavaScript code may be located
  • In the head - executed when called
  • In the body - executed while loading
  • In an external file called from either the head or the body e.g. <script src=“abc.js”></script>

• 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 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.

• 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, \', \&,
  

• 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