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JavaScript - add value to Set and return true on success or false on fail
3 points
In this article, we would like to show you how to add value to Set and return true on success or false on fail in JavaScript.
Quick solution:
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const set = new Set();2
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if (set.size !== (set.add('Some value ...'), set.size)) {4
console.log('Some value added!');5
}
In this example, we check the set size before and after adding a value to it. If the sizes are the same, it means the element hasn't been added and the function returns false, otherwise returns true.
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const addValue = (set, value) => set.size !== (set.add(value), set.size);2
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// Usage example:5
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const set = new Set();7
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console.log(addValue(set, 'a')); // true9
console.log(addValue(set, 'a')); // false10
console.log(addValue(set, 'b')); // true11
console.log(addValue(set, 'c')); // true
In this example, we use has() method to check whether an element with the specified value exists in a Set object. If the value exist, it means the element can't be added and the function returns false, otherwise returns true.
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const addValue = (set, value) => set.has(value) ? false : (set.add(value), true);2
// or: const addValue = (set, value) => !set.has(value) && (set.add(value), true);3
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// Usage example:6
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const set = new Set();8
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console.log(addValue(set, 'a')); // false10
console.log(addValue(set, 'a')); // true11
console.log(addValue(set, 'b')); // false12
console.log(addValue(set, 'c')); // false
