The old adage goes that you should pick the right tool for the job. ES6 promises provide the basics. If all you ever want or need is the basics, then that should/could work just fine for you. But, there are more tools in the tool bin than just the basics and there are situations where … Read more
render() method should render UI from this.props and this.state, so to asynchronously load data, you can use this.state to store imageId: imageUrl mapping. Then in your componentDidMount() method, you can populate imageUrl from imageId. Then the render() method should be pure and simple by rendering the this.state object Note that the this.state.imageUrls is populated asynchronously, … Read more
How a promise library decides If it has a .then function – that’s the only standard promise libraries use. The Promises/A+ specification has a notion called thenable which is basically “an object with a then method”. Promises will and should assimilate anything with a then method. All of the promise implementation you’ve mentioned do this. … Read more
How a promise library decides If it has a .then function – that’s the only standard promise libraries use. The Promises/A+ specification has a notion called thenable which is basically “an object with a then method”. Promises will and should assimilate anything with a then method. All of the promise implementation you’ve mentioned do this. … Read more
this is always the object the method is called on. However, when passing the method to then(), you are not calling it! The method will be stored somewhere and called from there later. If you want to preserve this, you will have to do it like this: .then(() => this.method2()) or if you have to … Read more
Here’s a reusable function that I think is pretty clear. var Q = require(“q”); // `condition` is a function that returns a boolean // `body` is a function that returns a promise // returns a promise for the completion of the loop function promiseWhile(condition, body) { var done = Q.defer(); function loop() { // When … Read more
In javascript there are no block-level scopes only function-level scopes: Read this article about javaScript Scoping and Hoisting. See how I debugged your code: var deferred = $q.defer(); deferred.count = i; console.log(deferred.count); // 0,1,2,3,4,5 –< all deferred objects // some code .success(function(data){ console.log(deferred.count); // 5,5,5,5,5,5 –< only the last deferred object deferred.resolve(data); }) When you … Read more
In simple terms, inside a then handler function: A) When x is a value (number, string, etc): return x is equivalent to return Promise.resolve(x) throw x is equivalent to return Promise.reject(x) B) When x is a Promise that is already settled (not pending anymore): return x is equivalent to return Promise.resolve(x), if the Promise was … Read more
Use a pattern along these lines: function getValue(file) { return lookupValue(file); } getValue(‘myFile.txt’).then(function(res) { // do whatever with res here }); (although this is a bit redundant, I’m sure your actual code is more complicated)
but instead they are being output immediately for some reason. You are calling them already here: promiseFuncs.push(getDelayedString(str)); // ^^^^^ You would need to push function(){ return getDelayedString(str); }. Btw, instead of using pushing to an array in an each loop you rather should use map. And actually you don’t really need that anyway but can … Read more