十五的学习日记20161003-promise相关

十五的学习日记20161003

JavaScript

1. 还是promise.
   昨天没写完,今天好好写.
   promise的关键在于,每一步都要构造并返回promise对象.
   示例代码

// 0.5秒后返回input*input的计算结果:
function multiply(input) {
    return new Promise(function (resolve, reject) {
        console.log('calculating ' + input + ' x ' + input + '...');
        setTimeout(resolve, 500, input * input);
    });
}

// 0.5秒后返回input+input的计算结果:
function add(input) {
    return new Promise(function (resolve, reject) {
        console.log('calculating ' + input + ' + ' + input + '...');
        setTimeout(resolve, 500, input + input);
    });
}

var p = new Promise(function (resolve, reject) {
    console.log('start new Promise...');
    resolve(123);
});

p.then(multiply)
 .then(add)
 .then(multiply)
 .then(add)
 .then(function (result) {
    console.log('Got value: ' + result);
});