一组小清新的promise风格小函数

lightpromise.js

        function get(uri) {
            return http(uri,'GET');
        }
        function post(uri,data) {
            if(typeof data === 'object' && !(data instanceof String || (FormData && data instanceof FormData))) {
                var params = [];
                for(var p in data) {
                    if(data[p] instanceof Array) {
                        for(var i = 0; i < data[p].length; i++) {
                            params.push( encodeURIComponenet(p) + '[]=' + encodeURIComponenet(data[p][i]);
                        }
                    } else {
                        params.push( encodeURIComponenet(p) + '=' + encodeURIComponenet(data[p]);
                    }
                }
                data = params.join('&');
            }
            return http(uri,'POST',data);
        }
        function http(uri,method,data) {
            return new Promise(function(resolve, reject) {
                var xhr = new XMLHttpRequest();
                xhr.open(method,uri,true);
                xhr.send(data);
                xhr.addEventListener('readystatechange',function(e){
                    if(xhr.readyState === 4) {
                        if(xhr.status === 200) {
                            resolve(xhr.responseText);
                        } else {
                            reject(xhr);
                        }
                    }
                })
            })
        }
        function wait(duration) {
            return new Promise(function(resolve, reject) {
                setTimeout(resolve,duration);
            })
        }
        function waitFor(element, event, useCapture){
            return new Promise(function(resolve, reject) {
                element.addEventListener(event, function listener(event){
                    resolve(event)
                    this.removeEventListener(event, listener, useCapture);
                },useCapture)
            })
        }
        function loadImage(src) {
            return new Promise(function(resolve, reject) {
                var image = new Image;
                image.src = src;
                image.addEventListener('load',function() {
                    resolve(image);
                });
                image.addEventListener('error',reject);
            })
        }
        function runScript(src) {
            return new Promise(function(resolve, reject) {
                var script = document.createElement('script');
                script.src = src;
                script.addEventListener('load',resolve);
                script.addEventListener('error',reject);
                (document.getElementsByTagName('head')[0] || document.body || document.documentElement).appendChild(script);
            })
        }

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