lesson 15: A Search Function

declare可用于只声明函数头而不声明函数体

type Result = {
    title: string,
    url: string,
    abstract: string
}
declare function search(
    query: string,
    tags?: string[]
): Result[]
search('Ember')
search('Ember', ['JS', 'TS'])

fetch

fetch返回一个promise, 类型是Promise

function search(query: string, tags?: string[]) {
    let queryString = `?query=${query}`
    if (tags && tags.length) {
        queryString += `&tags=${tags.join()}`
    }
    return fetch(`/search${queryString}`)
        .then(response => response.json() as Promise<Result[]>)
}

或者在函数头指明返回类型

function search(query: string, tags?: string[]): Promise<Result[]> {
    let queryString = `?query=${query}`
    if (tags && tags.length) {
        queryString += `&tags=${tags.join()}`
    }
    return fetch(`/search${queryString}`)
        .then(response => response.json())
}