Pure JavaScript: a function like jQuery’s isNumeric()
There’s no isNumeric() type of function, but you could add your own: NOTE: Since parseInt() is not a proper way to check for numeric it should NOT be used.
javascript
React with ES7: Uncaught TypeError: Cannot read property ‘state’ of undefined
Make sure you’re calling super() as the first thing in your constructor. You should set this for setAuthorState method Another alternative based on arrow function:
What is prevState in ReactJS? [duplicate]
prevState is a name that you have given to the argument passed to setState callback function. What it holds is the value of state before the setState was triggered by React; Since setState does batching, its sometimes important to know what the previous state was when you want to update the new state based on the previous state value. So … Read more
How do you round to 1 decimal place in Javascript?
Math.round(num * 10) / 10 works, here is an example… if you want it to have one decimal place, even when that would be a 0, then add… EDIT: Add round with precision function… Using this principle, for reference, here is a handy little round function that takes precision… … usage … … defaults to round … Read more
Getting “TypeError: failed to fetch” when the request hasn’t actually failed
The issue could be with the response you are receiving from back-end. If it was working fine on the server then the problem could be with the response headers. Check the Access-Control-Allow-Origin (ACAO) in the response headers. Usually react’s fetch API will throw fail to fetch even after receiving response when the response headers’ ACAO and the … Read more
Generate pdf from HTML in div using Javascript
jsPDF is able to use plugins. In order to enable it to print HTML, you have to include certain plugins and therefore have to do the following: Go to https://github.com/MrRio/jsPDF and download the latest Version. Include the following Scripts in your project: jspdf.js jspdf.plugin.from_html.js jspdf.plugin.split_text_to_size.js jspdf.plugin.standard_fonts_metrics.js If you want to ignore certain elements, you have to mark them … Read more
Get the current year in JavaScript
Create a new Date() object and call getFullYear(): Example usage: a page footer that always shows the current year: Run code snippetExpand snippet See also, the Date() constructor’s full list of methods.
Getting Unexpected Token Export
I am trying to run some ES6 code in my project but I am getting an unexpected token export error.
How to resolve TypeError: Cannot convert undefined or null to object
Generic answer This error is caused when you call a function that expects an Object as its argument, but pass undefined or null instead, like for example As that is usually by mistake, the solution is to check your code and fix the null/undefined condition so that the function either gets a proper Object, or does not get called at all. Answer specific to … Read more
How do I check for null values in JavaScript?
Javascript is very flexible with regards to checking for “null” values. I’m guessing you’re actually looking for empty strings, in which case this simpler code will work: Which will check for empty strings (“”), null, undefined, false and the numbers 0 and NaN Please note that if you are specifically checking for numbers it is a common mistake to miss 0 with this method, … Read more