Source: https://blog.csdn.net/honey199396/article/details/80750408

Array is a very simple data structure, but every time you use TypeScript array, you always forget how to use it. Just make it dry and forget to come and have a look.

1, Declaration of array

let array1:Array<number>;
let array2:number[];

 

2, Array initialization

let array1:Array<number> = new Array<number>();
let array2:number[] = [1，2，3];

 

3, Array element assignment, addition, change

let array:Array<number> = [1,2,3,4];
console.log(array)      // [1, 2, 3, 4]

array[0] = 20;          // modify
console.log(array)      // [20, 2, 3, 4]

array[4] = 5;           // assignment
console.log(array)      // [20, 2, 3, 4, 5]

array.push(6);          // Add to
console.log(array)      // [20, 2, 3, 4, 5, 6]

array.unshift(8, 0);    // Add in the first place
console.log(array);     // [8, 0, 20, 2, 3, 4, 5, 6]

 

Four, delete

let array:Array<number> = [1,2,3,4];
console.log(array)      // [1, 2, 3, 4]

let popValue = array.pop();     // Eject
console.log(array)      // [1, 2, 3]

array.splice(0, 1);     // Delete element (index, deleteCount)
console.log(array)      // [2, 3]

array.shift();          // Delete first element
console.log(array);     // [3]

 

5, Merging and breaking arrays

/**
  * Combines two or more arrays.
  * @param items Additional items to add to the end of array1.
  */
concat(...items: T[][]): T[];
/**
  * Combines two or more arrays.
  * @param items Additional items to add to the end of array1.
  */
concat(...items: (T | T[])[]): T[];
/**
 * This method returns a new array of specified starting positions
 */
slice(start?: number, end?: number): T[];

 

let array: Array<number> = [1, 2, 3];
let array2: Array<number> = [4, 5, 6];
let arrayValue = 7;
array = array.concat( array2);
console.log(array)          // [1, 2, 3, 4, 5, 6]

array = array.concat(arrayValue);
console.log(array)          // [1, 2, 3, 4, 5, 6, 7]

let newArray = array.slice(2, 4);
console.log(newArray)      // [3, 4]

 

6, Find array element location

/**
  * Returns the location of the first element found
  */
indexOf(searchElement: T, fromIndex?: number): number;
/**
  * Returns the location of the first element found in reverse order
  */
lastIndexOf(searchElement: T, fromIndex?: number): number;

 

let array: Array<string> = ["a","b","c","d","c","a"];
let indexC = array.indexOf("c");
console.log(indexC);            // 2
let lastA = array.lastIndexOf("a");
console.log(lastA);             // 5

 

7, Connect array elements

/**
 * Linked array
 */
join(separator?: string): string;

 

let array: Array<string> = ["a","b","c","d","c","a"];
let result = array.join();
console.log(result);            // a,b,c,d,c,a

result = array.join("+");
console.log(result);            // a+b+c+d+c+a

result = array.join("");
console.log(result);            // abcdca

 

8, Sort, reverse array

let array:Array<number> = [3, 2, 1, 8, 7, 0, 4];
console.log(array);             // [3, 2, 1, 8, 7, 0, 4]

array.sort();
console.log(array);             // [0, 1, 2, 3, 4, 7, 8]

array.reverse();
console.log(array);             // [8, 7, 4, 3, 2, 1, 0]

 

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