You could use Array#filter
with looking into the nested arrays by using Array#some
.
If the tag is found in a nested array, then iteration stops and the result is given back to the filter callback.
var array = [{ category: 'Business', users: [{ name: 'Sally', tags: [{ tag: 'accounting' }, { tag: 'marketing' }] }, { name: 'Bob', tags: [{ tag: 'sales' }, { tag: 'accounting' }] }] }, { category: 'Heritage', users: [{ name: 'Linda', tags: [{ tag: 'Italy' }, { tag: 'Macedonia' }] }, { name: 'George', tags: [{ tag: 'South Africa' }, { tag: 'Chile' }] }] }],
tag = 'marketing',
result = array.filter(a => a.users.some(u => u.tags.some(t => t.tag.includes(tag))));
console.log(result);
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