What is the function
Defined section of code, and the code blocks can be used repeatedly
Function returns
Enhance the reusability of code, a code will be pre-defined, used only when needed to trigger
Block
Forming a relatively independent scope
grammar:
function function name (parameter list) {
Code block (function body);
return return value
}
Function name (function call)
End of the function:
After the program hit return, behind the return codes will no longer perform, and at most only one return value
For now, I have known function
isNaN（）
prompt（）
parseInt（）
parseFloat（）
charcodeAt（）
toString（）
Number（）
document.write（‘’）
toFixed（）
alert（）
console.log（）
What is the scope
A range, also known as life-cycle variables
JS in the scope of classification
1. function scope
This variable can only be accessed in the current scope, the current function is accessible
Variable using the var keyword in the body of the function is a local variable
2. The global scope
Once defined, the code can access anywhere
What is an array
Continuous memory storage space to store more data, unified name
Why use an array
Compile multiple arrays stored continuously maintain and query
how to use
1. Create an empty array
Can not start with a number, you can not use keywords and reserved words, you can use underscores, letters, numbers and $
was = array [];
If this was [] it is to create a new array
2. Create an empty array of a number of known data
Create an array to store already exists but does not currently know of contents
var a = new Array (positive integer);
3. Create an array of content initialize an array at the same time
var name = [ ' ' , ' ' , ' ' ];
Direct input array quotes
How to Access
By subscript subscripted array element number stored in a location, default scratch, will not be repeated continuously
feature
Does not limit the type of data storage elements, the out of range target, the number of array elements
.length properties, recording the number of array theory, the last element is +1, because the first array is 0
How to add a new element to the end of the array
array [array.length] = 'element name';
Gets the last element of the inverse of the n-th element
array[array.length - n ];
Iterate perform the same operation on each element of the array
var drinks = [ "pearl milk tea", "ice tea", "plum", "happy fat house water"];
Read operation
for(var i = 0;i< drinks.length;i++){
console.log(drink[i]);
}
A cycle length of 10 to random assignment of data
var nums = new Array(10);
for(var i =0 ;i<nums.length;i++){
nums[i] = (Math.random()*10) | 0;
}
console.dir(nums);
Primitive types: number string boolean undefiend null
Local data directly stored in the variable data types
Passed by value: when the assignment between two variables or variable as a parameter passed to the function, in fact, only the value of the original variable assignment to a copy of the
The other party to modify the new variables will not affect the original variable values
Reference types: Data can not be saved directly in the data type of the local variable
Because the variable is allowed to save a value, and reference types are often simultaneously hold multiple values
It will be outside the window object, creating a separate memory space, and each individual has a unique storage space
Variable still preserved is a value, but only to save the array address it - called reference
Delivery is the address (actually passed by value, but the value is an address): Modify the new array, equivalent to directly modify the elements of the array