1. always declare variables with "var"; Without "var" the variable gets placed in the global context, and could override existing values
2. always use semicolons
3. always use curly braces; even for 1-line code
4. do not use eval(), with() and void()
5. always use '===' and '!==' instead of '==' and '!='
6. always use radix param in parseInt('09', 10);
7. use Number('8.5') to convert string to number
8. declare arrays like this: var arr = [1, 2, 3];
9. declare object like this: var obj = {a: 0, b: 1};
10. do not modify prototypes of builtin objects
11. use single quote (') instead of double quote (") in strings

• Google javascript style guide

javascript code conventions

var a = 5, b = 10;
var arr = [], obj = {};

if (a === b) {
    console.log('a === b');
} else { // not equals
    console.log('a !== b');
}

for (i = 0; i < arr.length; i += 1) {
	console.log(i);
}

function f() {
    return true;
}

f = function (e) {
    return true;
};

obj = {
	method: function () {
		return this.data;
	},
	data: 0
};

• javascript code conventions