Detailed explanation of javascript data types and git usage code

Data type

underfined, null, 0, false, NaN, empty string. Their logical negation results are all true.

Closure format

Benefits: Avoid naming conflicts (global variable pollution).

(function(a, b) {
console.log(a+b); //30
})(10, 20);

Intercept and clear the array

var arr = [12, 222, 44, 88];
arr.length = 2; //截取，arr = [12, 222]; 
arr.length = 0; //清空，arr will be equal to [].

Get the maximum and minimum values ​​of the array

var numbers = [5, 45822, 120, -215];
var maxInNumbers = Math.max.apply(Math, numbers); //45822
var minInNumbers = Math.min.apply(Math, numbers); //-215

Floating point calculation problem

0.1 + 0.2 == 0.3 //false

Why? Because 0.1+0.2 is equal to 0.30000000000000004. JavaScript numbers are constructed according to the IEEE 754 standard and are internally represented as 64-bit floating point decimals. This problem can be solved by using toFixed().

Array sort sort function

var arr = [1, 5, 6, 3]; //数字数组
arr.sort(function(a, b) {
return a - b; //从小到大排
return b - a; //从大到小排
return Math.random() - 0.5; //数组洗牌
});
var arr = [{ //对象数组
num: 1,
text: 'num1'
}, {
num: 5,
text: 'num2'
}, {
num: 6,
text: 'num3'
}, {
num: 3,
text: 'num4'
}]; 
arr.sort(function(a, b) {
return a.num - b.num; //从小到大排
return b.num - a.num; //从大到小排
});

Conversion of objects and strings

var obj = {a: 'aaa', b: 'bbb'};
var objStr = JSON.stringify(obj); // "{"a":"aaa","b":"bbb"}"
var newObj = JSON.parse(objStr); // {a: "aaa", b: "bbb"}

git notes

git uses the previous configuration

1.git config --global user.email xxx@163.com

2.git config --global user.name xxx

3.ssh-keygen -t rsa -C xxx@163.com (email address) // Generate ssh

4. Found. Open the ssh folder, use cat id_rsa.pub //Open the public key ssh string

5. Log in to github, settings - SSH keys - add ssh keys (just add all the above content)

Note: Then the account corresponding to this email address (xxxxx@gmail.com) will have permission to operate the warehouse on github. You can freely perform the following git commands.

Common git commands

1. git config user.name / user.email //View the current git user name and email

2. git clone project //Clone the warehouse locally.

3. Modify the local code and submit it to the branch: git add file / git commit -m "New file"

4. Push the local library to the remote library: git push origin master

5. View the commit log: git log -5

6. Return to a certain version: git reset --hard 123

7. Branch: git branch / git checkout name / git checkout -b dev

8. Merge the name branch to the current branch: git merge name / git pull origin

9. Delete the local branch: git branch -D name

10. Delete the remote branch: git push origin :daily/x.x.x

11. git checkout -b mydev origin/daily/1.0.0 //Map the remote daily branch to the local mydev branch for development
12. Merge the remote branch to the current branch git pull origin daily/1.1.1

13. Publish online:

git tag publish/0.1.5
git push origin publish/ 0.1.5:publish/0.1.5

14. Online code coverage to local:

git checkout --theirs build/scripts/ddos
git checkout -- theirs src/app/ddos

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