So you may want to rewrite your code as follows: function contains(a, obj) )) //falseĬonsole.log(. If you need the best performance, benchmark for yourself in the relevant execution environments.Īs others have said, the iteration through the array is probably the best way, but it has been proven that a decreasing while loop is the fastest way to iterate in JavaScript. If you need an easy solution, look for other answers. It might not be relevant to modern JS execution contexts. The promised performance improvement was based on a benchmark done in browsers of that time. Deleted elements are not visited.Update from 2019: This answer is from 2008 (11 years old!) and is not relevant for modern JS usage. If an existing, yet-unvisited element of the array is changed by callbackFn, its value passed to the callbackFn will be the value at the time that element gets visited.Second, use the array.some () method to find the searched object by property values. Changes to already-visited indexes do not cause callbackFn to be invoked on them again. To check if an array contains an object, you follow these steps: First, create a helper function that compares two objects by their properties.Syntax includes(keyword) includes(keyword, index) Parameter The function takes two parameters.
Hence, it is best suited in if condition checks. callbackFn will not visit any elements added beyond the array's initial length when the call to some() began. includes () Function to Check if Array Contains Value in JavaScript The includes () function of JavaScript checks whether a given element is present in an array.Note, however, that the length of the array is saved before the first invocation of callbackFn. Some() does not mutate the array on which it is called, but the function provided as callbackFn can. It is not invoked for empty slots in sparse arrays. In particular, for an empty array, it returns false for any condition.ĬallbackFn is invoked only for array indexes which have assigned values. Some() acts like the "there exists" quantifier in mathematics.
Otherwise, if callbackFn returns a falsy value for all elements, some() returns false. If such an element is found, some() immediately returns true and stops iterating through the array. It calls a provided callbackFn function once for each element in an array, until the callbackFn returns a truthy value. The some() method is an iterative method.
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