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DescriptionEdit
Common gotchas in Javascript
In this collection we are dealing with the problems of null, falsy, undefined, and 0.
You might be hitting errors like:
TypeError: Cannot read property 'length' of undefined
Uncaught TypeError: undefined is not a function
TypeError: reduce of empty array with no initial value
And you will be thinking about questions like:
- How do I check length safely?
- How do I safely use reduce after a method like filter that has returned an empty array?
- How do I say 'or this', if the first doesn't exist?
- How do I set a default or fallback value?
- How is null safety handled in JavaScript?
Some tools you will need:
if(myVar && myVar.length).reduce((sum, value) => sum + value, 0)||function multiply(a, b = 1)===
And some tools to know about, but might not be available on this platform: