1. 泛型定义

泛型（Generics）指在定义函数、接口、类的时候，不预先指定具体的类型，而在使用的时候再指定类型的一种特性。

2.应用实例

  1. function createArray(length: number, value: any): Array<any> {
  2.     let result = [];
  3.     for (let i = 0; i < length; ++i) {
  4.         result[i] = value;
  5.     }
  6.     return result;
  7. }
  9. //result: ['x','x','x']
  10. console.log('array: ', createArray(3, 'x'));
  1. function arrayGen<T>(length: number, value: T): Array<T> {
  2.     let result = [];
  3.     for (let i = 0; i < length; ++i) {
  4.         result[i] = value;
  5.     }
  6.     return result;
  7. }
  8. //result: ['x','x','x']
  9. console.log('array: ', arrayGen<string>(3, 'x'));
  1. function swap<T, U>(tuple: [T, U]): [U, T] {
  2.     return [tuple[1], tuple[0]]
  3. }
  5. //result['six',6]
  6. swap([6, 'six']);

3.泛型约束

  1. interface LengthWise {
  2.     length: number;
  3. }
  5. function loggingIdentity<T extends LengthWise>(arg: T): T {
  6.     console.log('length:', arg.length);
  7.     return arg;
  8. }
  10. // - error TS2345: Argument of type 'number' is not assignable to parameter of type 'LengthWise'.
  11. loggingIdentity(7);
  12. loggingIdentity("a");
  14. function copyField<T extends U, U>(target: T, source: U): T {
  15.     for (let id in source) {
  16.         target[id] = (<T>source)[id]
  17.     }
  18.     return target;
  19. }
  21. let x = { a: 1, b: 2, c: 3, d: 4 }
  22. copyField(x, { b: 10, d: 32 })

4.泛型接口

  2. interface SearchFun {
  3.     (source: string, substring: string): boolean;
  4. }
  6. let mySearch: SearchFun;
  7. mySearch = function (source: string, substring: string) {
  8.     return source.search(substring) !== -1;
  9. }
  11. interface ArrayGenFunc {
  12.     <T>(length: number, value: T): Array<T>;
  13. }
  15. let newArray: ArrayGenFunc;
  16. newArray = function <T>(length: number, value: T): Array<T> {
  17.     let result: T[] = [];
  18.     for (let i = 0; i < length; ++i) {
  19.         result[i] = value;
  20.     }
  21.     return result;
  22. }
  24. newArray(3, 'x');
  26. interface ArrayGenFuncG<T>{
  27.     (length:number , value:T):Array<T>;
  28. }
  30. let a: ArrayGenFuncG<any> ;
  31. a = function<T>(length:number, value:T):Array<T>{
  32.     let result:T[] = [] ;
  33.     for(let i = 0 ; i < length ; ++i){
  34.         result[i] =value ;
  35.     }
  36.     return result ;
  37. }
  39. a(3 , 'x');

5.泛型类

  1. class GenericNumber<T>{
  2.     zeroValue: T;
  3.     add: (x: T, y: T) => T;
  4. }
  6. let myGen = new GenericNumber<number>();
  7. myGen.zeroValue = 0;
  8. console.log('add:' + myGen.add(1, 2));

6.泛型参数默认类型

  1. function createArr<T = string>(length: number, value: T): Array<T> {
  2.     let result: T[] = [];
  3.     for (let i = 0; i < length; ++i) {
  4.         result[i] = value;
  5.     }
  6.     return result;
  7. }
  9. console.log(createArr(2, 'x'));