# Reference
Examples are better than 1000 words.——一例胜千言
### 引用
\\
\\
\
```javascript
```
### 输出
* innerHTML
```javascript
document.getElementById("demo").innerHTML='Hello World!';
```
* document.write()
* window\.alert()
* console.log()
* print()
### 控制
* getElementById("demo")
* getElementsByClassName("demo")
* getElementsByTagName("p")
* querySelectorAll("p.intro")
### 声明
* var
* let
* cost
### 注释
* //单行注释
* /\*多行注释\*/
### 运算符
* \+
* \-
* \*
* \*\*
* /
* %
* ++
* \--
* &&
* ||
* !
* \==
* \===
* !=
* !==
* \>
* <
* \>=
* <=
* ?
* +=
* -=
* \*=
* /=
* %=
* \*\*=
### 函数
```javascript
function myFunction(p1, p2) {
return p1 * p2; // The function returns the product of p1 and p2
}
```
* 数组：x = \["a","b","c"]
* 物体：x={name:"fiat",model:"modern",color:"white"}
### 字符串处理
* .length
* indexOf()
* lastIndexOf()
* search()
* slice()
* substring()
* substr()
* replace()
* toUpperCase()
* toLowerCase()
* concat()
* trim()
* charAt()
* charCodeAt()
* split()
### 数字
Js语法中，支持数位是15位，以及小数点后17位。
NaN = not a number
isNaN()
数字进制
```javascript
var myNumber = 32;
myNumber.toString(10); // returns 32
myNumber.toString(32); // returns 10
myNumber.toString(16); // returns 20
myNumber.toString(8); // returns 40
myNumber.toString(2); // returns 100000
```
数字变成物体
```javascript
var x = new Number(124);
```
* toExponential()
* toFixed()
* toPrecision()
### 数组
```javascript
var cars = ["Saab", "Volvo", "BMW"];||var cars = new Array("Saab", "Volvo", "BMW");
```
* array.foreach()
* array.push()
* array.pop()
* typeof.array
* array.join("\*")
* array.shift()
* array.unshift()
* delete array\[0]
* array.splice(2,0,"apple","orange")
* array.concat(array)
* sort()
* reverse()
调用
```javascript
person.lastName;||person["lastName"];
```
### 时间
* Date(year, month, day, hours, minutes, seconds, milliseconds)
* toUTCString()
* toISOString()
* toDateString()
| getFullYear() | Get the **year** as a four digit number (yyyy) |
| ----------------- | ------------------------------------------------- |
| getMonth() | Get the month as a number (0-11) |
| getDate() | Get the day as a number (1-31) |
| getHours() | Get the hour (0-23) |
| getMinutes() | Get the minute (0-59) |
| getSeconds() | Get the second (0-59) |
| getMilliseconds() | Get the millisecond (0-999) |
| getTime() | Get the time (milliseconds since January 1, 1970) |
| getDay() | Get the weekday as a number (0-6) |
| Date.now() | Get the time. ECMAScript 5. |
| Method | Description |
| -------------------- | ----------------------------------------------------------- |
| getUTCDate() | Same as getDate(), but returns the UTC date |
| getUTCDay() | Same as getDay(), but returns the UTC day |
| getUTCFullYear() | Same as getFullYear(), but returns the UTC year |
| getUTCHours() | Same as getHours(), but returns the UTC hour |
| getUTCMilliseconds() | Same as getMilliseconds(), but returns the UTC milliseconds |
| getUTCMinutes() | Same as getMinutes(), but returns the UTC minutes |
| getUTCMonth() | Same as getMonth(), but returns the UTC month |
| getUTCSeconds() | Same as getSeconds(), but returns the UTC seconds |
| Method | Description |
| ----------------- | ------------------------------------------------- |
| setDate() | Set the day as a number (1-31) |
| setFullYear() | Set the year (optionally month and day) |
| setHours() | Set the hour (0-23) |
| setMilliseconds() | Set the milliseconds (0-999) |
| setMinutes() | Set the minutes (0-59) |
| setMonth() | Set the month (0-11) |
| setSeconds() | Set the seconds (0-59) |
| setTime() | Set the time (milliseconds since January 1, 1970) |
### 数学
* Math.PI
* Math.round()
* Math.pow()
* Math.sqrt()
* Math.abs()
* Math.ceil()
* Math.floor()
* Math.sin()
* Math.cos()
* Math.min()
* Math.max()
* Math.random()
* Math.E
* Math.SQRT2
* Math.SQRT1\_2
* Math.LN2
* Math.LN10
* Math.LOG2E
* Math.LOG10E
### 逻辑
### 逻辑
True or False
```javascript
if (condition) {
// block of code to be executed if the condition is true
} else {
// block of code to be executed if the condition is false
}
```
* Boolean()
* variablename = (condition) ? value1:value2
```javascript
if (condition1) {
// block of code to be executed if condition1 is true
} else if (condition2) {
// block of code to be executed if the condition1 is false and condition2 is true
} else {
// block of code to be executed if the condition1 is false and condition2 is false
}
```
```javascript
switch(expression) {
case x:
// code block
break;
case y:
// code block
break;
default:
// code block
}
```
```javascript
switch (new Date().getDay()) {
case 6:
text = "Today is Saturday";
break;
case 0:
text = "Today is Sunday";
break;
default:
text = "Looking forward to the Weekend";
}
```