istanbul-js/index.js

use localStorage to cache script

/**
 * use localStorage to cache script
 * @author: zee
 * @date: 2016-12-12
 */

;(function (sources) {
    var KEY_CACHE = 'js_script_cache',
        KEY_VERSION = 'js_script_version',
        KEY_CONTENT = 'js_script_content';

    var getScriptInfo = function (src) {
        var items = src.split('.');
        var currVersion = items[items.length - 2];
        var scriptName = items[items.length - 4];
        if (currVersion.indexOf('/') !== -1) {
            currVersion = scriptName = '';
        }
        return {
            currVersion: currVersion,
            scriptName: scriptName,
        };
    };

    var cacheScript = function (script, src, scriptInfo) {
        var body = document.getElementsByTagName('body')[0];
        var xhr = new XMLHttpRequest();
        xhr.open('GET', src);
        xhr.onreadystatechange = function () {
            if (xhr.readyState === 4 && xhr.status === 200) {
                try {
                    script.innerHTML = xhr.responseText;
                    body.appendChild(script);
                    if (scriptInfo.scriptName) {
                        var result = JSON.parse(localStorage.getItem(KEY_CACHE)) || {};
                        var temp = result[scriptInfo.scriptName] = {};
                        temp[KEY_VERSION] = scriptInfo.currVersion;
                        temp[KEY_CONTENT] = xhr.responseText;
                        localStorage.setItem(KEY_CACHE, JSON.stringify(result));
                    }
                } catch (e) {
                }
            }
        };
        xhr.send();
    }

    var load = function (src) {
        var scriptContent,
            script = document.createElement('script'),
            body = document.getElementsByTagName('body')[0],
            scriptInfo = getScriptInfo(src),
            oriScript = JSON.parse(localStorage.getItem(KEY_CACHE)),
            oriVersion = oriScript && oriScript[scriptInfo.scriptName] && oriScript[scriptInfo.scriptName][KEY_VERSION] || '';

        script.type = 'text/javascript';

        if (oriVersion && scriptInfo.currVersion === oriVersion) {
            try {
                scriptContent = oriScript[scriptInfo.scriptName][KEY_CONTENT];
                script.innerHTML = scriptContent;
                body.appendChild(script);
            } catch (e) {
                cacheScript(script, src, scriptInfo);
            }
        } else {
            cacheScript(script, src, scriptInfo);
        }
    };

    sources.forEach(function(src) {
        load(src);
    });

})(["${data.vendor}", "${data.page}"]);