JavaScript tips for using

1 underfined, NULL, 0, False, NaN, empty string logical result is False


2 getting members randomly from an array
var items = [548, ' a ', 2, 5478, ' foo ', 8852,, ' Doe ', 2145, 119];
var Randomitem = Items[math.floor (Math.random () * items.length)];


3 Gets the random number in the specified range
var x = Math.floor (Math.random () * (Max-min + 1)) + min;


4 Gets the maximum and minimum values in the array
var numbers = [5, 458, 120,-215, 228, 400, 122205,-85411];
var maxinnumbers = Math.max.apply (Math, numbers);
var mininnumbers = Math.min.apply (Math, numbers);


5 emptying the array
var myArray = [12, 222, 1000];
myarray.length = 0; MyArray'll is equal to [].


6 Do not delete or remove elements directly from the array
Avoid:
var items = [548, ' a ', 2, 5478, ' foo ', 8852,, ' Doe ', 2154, 119];
Items.length; Return 11
Delete Items[3]; return True
Items.length; Return 11
/* Items results for [548, "a", undefinedx1, 5478, "foo", 8852, Undefinedx1, "Doe", 2154, 119] */


Instead, you should:
var items = [548, ' a ', 2, 5478, ' foo ', 8852,, ' Doe ', 2154, 119];
Items.length; Return 11
Items.splice (3,1);
Items.length; Return 10
/* Items results for [548, "a", 5478, "foo", 8852, Undefinedx1, "Doe", 2154, 119]
You can use delete when you delete an object's properties.
*/


7 using logic with or in conditions
Logic or can also be used to set default values, such as default values for function parameters.


function DoSomething (arg1) {
Arg1 = Arg1 | | 10; Arg1 would has ten as a default value if it ' s not already set
}


8 Checking the properties of an object through the for-in loop
The following usage can prevent the iteration from entering the object's prototype properties.


for (var name in object) {
if (Object.hasownproperty (name)) {
Do something with Name
}
}


9 serialization and deserialization with JSON
var person = {name: ' Saad ', age:26, department: {id:15, Name: ' R '}};
var Stringfromperson = json.stringify (person);
/* Stringfromperson result for ' {' name ': ' Saad ', ' age ': ', ' Department ': {' ID ': ' "Name ':" R/r}} "*/
var personfromstring = Json.parse (Stringfromperson);
/* The value of personfromstring is the same as the person object */


10 do not use for-in on arrays
Avoid:
var sum = 0;
for (var i in arraynumbers) {
Sum + = Arraynumbers[i];
}


But:
var sum = 0;
for (var i = 0, len = arraynumbers.length; i < Len; i++) {
Sum + = Arraynumbers[i];
}


Another benefit is that I and Len two variables are in the first declaration of the For Loop, and they are initialized only once, which is faster than this:
for (var i = 0; i < arraynumbers.length; i++)


11 primitive operators are faster than function calls


For example, generally don't do this:
var min = Math.min (A, b);
A.push (v);


This can be replaced by:
var min = a < b? A:B;
A[a.length] = v;






Reference:
Http://www.w3cschool.cc/w3cnote/js-45-tips.html

JavaScript tips for using