javascript - Is it possible cache node.js view output as a html file? -

in php, used use output buffering cache output , save html file. wondering if same done in node.js. following route file:

module.exports = {   index: function(section,page,req,res){   var l = res.locals,      db = l.db,    promise = l.promise,    promise.props({         my: db.db.query('call fetchdata()'),         amba: db.db.query("call fetchanother()")   }).then(function(obj){          return res.render(section+'.html',obj)      }).then(function(data){         console.log(data);         l.fs.writefile('index.html', data)      }).catch(function (error) {         console.log(error);     })  } }; 

return res.render(section+'.html',obj) isn't working. console.log(data) returns "undefined" in console , html file doesn't have word "undefined". have tried this:

    .then(function(obj){         var cache        res.render(section+'.html',obj,function(k,content){            res.send(content)            cache = content        })        return cache;     }).then(function(data){        console.log(data);        l.fs.writefile('index.html', data)      }) 

it still undefined. there way cache view result html file?

in 1st snippet, data undefined because that's value res.render(...) returns.

typically (depending on exact promise implementation), value other promise returned in .then() calback treated resolution value. so, following 2 snippets equivalent.

.then(function () {     return undefined; }) 

.then(function () {     return new promise(function (resolve) {         resolve(undefined);     }); }) 

to receive html, since res.render() asynchronous , doesn't provide promise itself, you'll want wrap in promise it's waited on:

.then(function(obj){     return new promise(function (resolve, reject) {         res.render(section+'.html', obj, function (err, html) {             if (err)                 reject(err);             else                 resolve(html);         });     }); }).then(function(data){     // ... 

note: above snippets compatible es6 promises , may require revisions if you're using different implementation.

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for 2nd snippet, there's q&a on explanation:

why variable unaltered after modify inside of function?