I’ve initialized a state that is an array, and when I update it my component does not re-render. Here is a minimal proof-of-concept: Based on this code, it seems that the input should contain the number 0 to start, and any time it is changed, the state should change too. After entering “02” …
Tag: javascript
Change value of a variable inside foreach loop? Make it available outside the loop
I’m setting an initial flag then doing a foreach which changes the flag to a different value but outside the foreach loop I still see the original flag. As if nothing changed. But it did change inside the foreach loop The value is only changed inside the foreach loop, but not outside of it.. I saw a num…
Unable to deploy Solidity contract to Rinkeby network (Invalid asm.js: Invalid member of stdlib)
I’ve been learning Solidity using this course by Stephen Grider and it’s been going well until now, where I am trying to deploy my code to the Rinkeby test network. For reference, I am using Node version 11.15.0 with npm version 6.7.0 with these dependencies: I have spent hours switching between v…
Rename keys with ramda js
expected output: I’m thinking the renamed keys are defined in an object (but fine if there’s a better way to map them): How can I do this with Ramda? Something with R.map Answer There is an entry in Ramda’s Cookbook for this: But with the ubiquity of ES6, it’s pretty easy to write this…
Valid Braces – CodeWars Challenge
There is a challenge on codewars that asks you to check whether a string of parentheses, brackets, and curly braces is valid. A string of braces is considered valid if all braces are matched with the correct brace. I.e. “()” is valid and “[(])” is not. “(){}[]” is valid and…
React Native FlatList with custom buttons, how to change color on click?
I have created a FlatList that renders names. Each row has its own button. When you click the button, the name is added to a list and the button should change color My problem is that the button does not change color as soon as I click on it, it only changes color when I make a pull refresh on
2 components almost identical to each other. The only difference is that each component has a different GET request. Merge them?
I currently have 2 components which are almost identical to each other. HTML structure and CSS rules are the same and the only difference is that on mounted() of these components, a different GET request is made. One gets all the visited places and one gets all wishlisted place. The response to both GET reque…
How to merge two objects, overriding null values?
I’d like to merge two similar but not identical objects and override null values in one of them, if such exist. For example I’d have these two objects: And the effect of merge should be: In other words, the most important source of data in the merged object is obj2 but it lacks some properties fro…
JavaScript seems to be doing floating point wrong (compared to C)
From everything I’ve been able to find online, JavaScript allegedly uses IEEE 754 doubles for its numbers, but I have found numbers that can work in C doubles, but not in JavaScript. For example, prints 131621703842267136.000000 NOTE: IN AN EARLIER VERSION OF THE QUESTION I COPPIED THE WRONG NUMBER FOR …
PERFORMANCE Accessing a parent using child.parentNode vs getElementById
I want to access the parent of an element. I can access the parent by using child.parentNode but I have the parent id so i can also access it by using getElementById() The question is: which way is better in terms of performance? And why is it better? Answer So, rather than speculating on this, I decided to l…