As mentioned in a previous article, JavaScript uses type coercion in Boolean contexts, such as conditionals. This means that values are considered either truthy or falsy depending on how they are evaluated in a Boolean context. Combining this with the Boolean
function and truth checking a collection of values becomes a breeze.
Check if all values in an array are truthy
Using Array.prototype.every()
, we can easily check if all values in an array are truthy. The Boolean
function can be used as a default callback to check if all values are truthy, but specifying a custom callback function is also possible.
代码实现
const all = (arr, fn = Boolean) => arr.every(fn);
all([4, 2, 3], x => x > 1); // true
all([1, 2, 3]); // true
Check if any values in an array are truthy
Using Array.prototype.some()
, we can check if any values in an array are truthy. The Boolean
function can be used as a default callback to check if any values are truthy, but specifying a custom callback function is also possible.
使用样例
const any = (arr, fn = Boolean) => arr.some(fn);
any([0, 1, 2, 0], x => x >= 2); // true
any([0, 0, 1, 0]); // true
Check if all values in an array are falsy
Similarly, Array.prototype.some()
can be used to check if any values in an array are falsy. Again, the Boolean
function can be used as the default callback, but you can also specify a custom callback function.
const none = (arr, fn = Boolean) => !arr.some(fn);
none([0, 1, 3, 0], x => x == 2); // true
none([0, 0, 0]); // true
Check if all objects have a given property
Taking this one step further, Array.prototype.every()
can be used to check if all objects in an array have a given property. This is useful for validating data, for example. Simply checking for the existence of a property will return a truthy or falsy value depending on whether the property exists or not.
const truthCheckCollection = (collection, pre) =>
collection.every(obj => obj[pre]);
truthCheckCollection(
[
{ user: 'Tinky-Winky', sex: 'male' },
{ user: 'Dipsy', sex: 'male' },
],
'sex'
); // true
翻译自:https://www.30secondsofcode.org/js/s/check-array-values-are-truthy