searchbad.blogg.se - Findindex in javascript

Look through the cheat sheet just to be aware of them. Return arr1.length = arr2.length & arr1.every((value, index) => value = arr2) Īlert( arraysEqual(, )) // trueĪrr.fill(value, start, end) – fills the array with repeating value from index start to end.Īrr.copyWithin(target, start, end) – copies its elements from position start till position end into itself, at position target (overwrites existing).Īrr.flat(depth)/ arr.flatMap(fn) create a new flat array from a multidimensional array.įrom the first sight it may seem that there are so many methods, quite difficult to remember. These methods behave sort of like || and & operators: if fn returns a truthy value, arr.some() immediately returns true and stops iterating over the rest of items if fn returns a falsy value, arr.every() immediately returns false and stops iterating over the rest of items as well. If any/all results are true, returns true, otherwise false. The function fn is called on each element of the array similar to map. But there are few others:Īrr.some(fn)/ arr.every(fn) check the array. These methods are the most used ones, they cover 99% of use cases. Please note that methods sort, reverse and splice modify the array itself. Array.isArray(value) checks value for being an array, if so returns true, otherwise false.reduce/reduceRight(func, initial) – calculate a single value over the array by calling func for each element and passing an intermediate result between the calls.split/join – convert a string to array and back.reverse() – reverses the array in-place, then returns it.sort(func) – sorts the array in-place, then returns it.map(func) – creates a new array from results of calling func for every element.

forEach(func) – calls func for every element, does not return anything.

findIndex is like find, but returns the index instead of a value.

find/filter(func) – filter elements through the function, return first/all values that make it return true.includes(value) – returns true if the array has value, otherwise false.indexOf/lastIndexOf(item, pos) – look for item starting from position pos, return the index or -1 if not found.If any of items is an array, then its elements are taken.

concat(.items) – returns a new array: copies all members of the current one and adds items to it.

slice(start, end) – creates a new array, copies elements from index start till end (not inclusive) into it.

items) – at index pos deletes deleteCount elements and inserts items.

unshift(.items) – adds items to the beginning.

shift() – extracts an item from the beginning,.

The latter is used more often, as it’s a bit easier to understand for most people. Return user.age >= this.minAge & user.age army.canJoin(user)), that does the same.