解构使得将数组中的值或对象中的属性解包为不同的变量成为可能。
优点
使代码简洁且更具可读性。我们可以轻松避免重复的解构表达式。
一些用例
从对象、数组中获取变量值。
let array = [1, 2, 3, 4, 5];let [first, second, ...rest] = array;console.log(first, second, rest);//expected output: 1 2 [3,4,5]let objectfoo = { foo: 'foo' };let { foo: newvarname } = objectfoo;console.log(newvarname);//expected output: foo// nested extractionlet objectfoobar = { foo: { bar: 'bar' } };let { foo: { bar } } = objectfoobar;console.log(bar);//expected output: bar
登录后复制仅更改对象中所需的属性。
let array = [ { a: 1, b: 2, c: 3 }, { a: 4, b: 5, c: 6 }, { a: 7, b: 8, c: 9 }, ]; let newarray = array.map(({ a, ...rest }, index) => ({ a: index + 10, ...rest, })); console.log(newarray);/* expected output: [ { "a": 10, "b": 2, "c": 3 }, { "a": 11, "b": 5, "c": 6 }, { "a": 12, "b": 8, "c": 9 }]*/
登录后复制将参数中的值提取到独立变量中。
// object destructuring: const objectdestructure = ({ property }: { property: string }) => { console.log(property); }; objectdestructure({ property: 'foo' }); //expected output: foo // array destructuring: const arraydestructure = ([item1, item2]: [string, string]) => { console.log(item1 , item2); }; arraydestructure(['bar', 'baz']); //expected output: bar baz// assigning default values to destructured properties: const defaultvaldestructure = ({ foo = 'defaultfooval', bar, }: { foo?: string; bar: string; }) => { console.log(foo, bar); }; defaultvaldestructure({ bar: 'bar' });//expected output: defaultfooval bar
登录后复制从对象中获取动态键值。
const obj = { a: 1, b: 2, c: 3 };const key = 'c';let { [key]: val } = obj;console.log(val);//expected output: 3
登录后复制交换值。
const b = [1, 2, 3, 4];[b[0], b[2]] = [b[2], b[0]]; // swap index 0 and 2console.log(b);//expected output : [3,2,1,4]
登录后复制获取对象的子集。
const obj = { a: 5, b: 6, c: 7 };const subset = (({ a, c }) => ({ a, c }))(obj);console.log(subset); // expected output : { a: 5, c: 7 }
登录后复制进行数组到对象的转换。
const arr = ["2024", "17", "07"], date = (([year, day, month]) => ({year, month, day}))(arr);console.log(date);/* expected output: { "year": "2024", "month": "07", "day": "17"} */
登录后复制在函数中设置默认值。
function somename(element, input, settings={i:"#1d252c", i2:"#fff", ...input}){ console.log(settings.i); console.log(settings.i2);}somename('hello', {i: '#123'});somename('hello', {i2: '#123'});/* expected output: #123#fff#1d252c#123 */
登录后复制获取数组长度、函数名称、参数数量等属性。
let arr = [1,2,3,4,5];let {length} = arr;console.log(length);let func = function dummyfunc(a,b,c) { return 'a b and c';}let {name, length:funclen} = func;console.log(name, funclen);/* expected output : 5dummyfunc 3*/
登录后复制组合数组或对象。
//combining two arraysconst alphabets = ['A','B','C','D','E','F'];const numbers = ['1','2','3','4','5','6'];const newArray = [...alphabets, ...numbers]console.log(newArray);//expected output: ['A','B','C','D','E','F','1','2','3','4','5','6']//combining two objectsconst personObj = { firstname: "John", lastname: "Doe"};const addressObj = { city: "some city", state: "some state" };const combinedObj = {...personObj, ...addressObj};console.log(combinedObj);/* expected output: { "firstname": "John", "lastname": "Doe", "city": "some city", "state": "some state"} */
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以上就是Typescript 中的 ESestructuring的详细内容，更多请关注【创想鸟】其它相关文章！
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