async/await 继发执行与并发执行，看如何控制
两个异步函数 foo bar
function foo() {return new Promise((resolve, reject) => {setTimeout(() => {console.log('foo:' + new Date().toLocaleString())resolve('foo')}, 2000)})}function bar() {return new Promise((resolve, reject) => {setTimeout(() => {console.log('bar:' + new Date().toLocaleString())resolve('bar')}, 2000)})}
继发执行
//继发执行async function main() {console.log('beginTime:' + new Date().toLocaleString())var foostr = await foo();console.log(new Date().toLocaleString())console.log(foostr);var barstr = await bar();console.log(new Date().toLocaleString())console.log(barstr);console.log('endTime:' + new Date().toLocaleString())}//继发执行async function main2() {let docs = [foo, bar];console.log('beginTime:' + new Date().toLocaleString())for (let doc of docs) {var str = await doc();console.log(new Date().toLocaleString())console.log(str);}console.log('endTime:' + new Date().toLocaleString())}
并发执行
//并发执行async function async_main() {console.log('beginTime:' + new Date().toLocaleString())let [get_foo, get_bar] = await Promise.all([foo(), bar()]);console.log(new Date().toLocaleString());console.log(get_foo);console.log(get_bar);console.log('endTime:' + new Date().toLocaleString())}//并发执行async function async_main4() {let docs = [foo(), bar()];console.log('beginTime:' + new Date().toLocaleString())for (let doc of docs) {var str = await doc;console.log(new Date().toLocaleString())console.log(str);}console.log('endTime:' + new Date().toLocaleString())}//并发执行async function async_main2() {console.log('beginTime:' + new Date().toLocaleString())let fooPromise = foo();let barPromise = bar();let get_foo = await fooPromise;console.log(new Date().toLocaleString());console.log(get_foo);let get_bar = await barPromise;console.log(new Date().toLocaleString());console.log(get_bar);console.log('endTime:' + new Date().toLocaleString())}
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