For a succinct modern cross-browser implementation, just do: function isNullOrWhitespace( input ) { return !input || !input.trim(); } Here’s the jsFiddle. Notes below. The currently accepted answer can be simplified to: function isNullOrWhitespace( input ) { return (typeof input === ‘undefined’ || input == null) || input.replace(/\s/g, ”).length < 1; } And leveraging falsiness, even … Read more
You should absolutely use isEmpty(). Computing the size() of an arbitrary list could be expensive. Even validating whether it has any elements can be expensive, of course, but there’s no optimization for size() which can’t also make isEmpty() faster, whereas the reverse is not the case. For example, suppose you had a linked list structure … Read more
As long as your selector is actually working, I see nothing wrong with your code that checks the length of the array. That should do what you want. There are a lot of ways to clean up your code to be simpler and more readable. Here’s a cleaned up version with notes about what I … Read more
Using not a to test whether a is None assumes that the other possible values of a have a truth value of True. However, most NumPy arrays don’t have a truth value at all, and not cannot be applied to them. If you want to test whether an object is None, the most general, reliable … Read more
If you’re dealing with optional Strings, this works: (string ?? “”).isEmpty The ?? nil coalescing operator returns the left side if it’s non-nil, otherwise it returns the right side. You can also use it like this to return a default value: (string ?? “”).isEmpty ? “Default” : string!
You can use the :placeholder-shown pseudo class. Technically a placeholder is required, but you can use a space instead. input:not(:placeholder-shown) { border-color: green; } input:placeholder-shown { border-color: red; } <input placeholder=”Text is required” /> <input placeholder=” ” value=”This one is valid” /> <input placeholder=” ” />
Misspellings are irritating, aren’t they? Check your spelling of empty, but then also try this: #!/bin/bash -e if [ -s diff.txt ]; then # The file is not-empty. rm -f empty.txt touch full.txt else # The file is empty. rm -f full.txt touch empty.txt fi I like shell scripting a lot, but one disadvantage of … Read more
In Bash at least the following command tests if $var is empty: if [[ -z “$var” ]]; then # Do what you want fi The command man test is your friend.
Both styles are used within the Go’s standard libraries. if len(s) > 0 { … } can be found in the strconv package: http://golang.org/src/pkg/strconv/atoi.go if s != “” { … } can be found in the encoding/json package: http://golang.org/src/pkg/encoding/json/encode.go Both are idiomatic and are clear enough. It is more a matter of personal taste and … Read more
Empty string, undefined, null, … To check for a truthy value: if (strValue) { // strValue was non-empty string, true, 42, Infinity, [], … } To check for a falsy value: if (!strValue) { // strValue was empty string, false, 0, null, undefined, … } Empty string (only!) To check for exactly an empty string, … Read more