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/**
* A mostly functional query filter similar to SQL's WHERE
* @param {Array} collection - Array of objects to filter
* @param {Object} properties - Object containing properties to match against
* @returns {Array} - Filtered array of objects
*/
const where = (collection, properties) => {
// null/undefined inputs
if (!collection || !properties) {
return [];
}
// Cache property paths and their split versions for performance
const propertyPaths = Object.entries(properties).map(([key, value]) => ({
path: key,
parts: key.split('.'),
value
}));
// An optimized nested value getter with memoization
const getNestedValue = (() => {
const cache = new WeakMap();
return (obj, parts) => {
if (!obj) return undefined;
let cached = cache.get(obj);
if (!cached) {
cached = new Map();
cache.set(obj, cached);
}
const pathKey = parts.join('.');
if (cached.has(pathKey)) {
return cached.get(pathKey);
}
const value = parts.reduce((current, key) =>
current && current[key] !== undefined ? current[key] : undefined,
obj
);
cached.set(pathKey, value);
return value;
};
})();
// An optimized equality comparison
const isEqual = (value1, value2) => {
// Handle null/undefined cases first for faster returns
if (value2 === undefined) return true;
if (value1 === value2) return true;
if (value1 === null || value2 === null) return false;
// Array comparison
if (Array.isArray(value1) && Array.isArray(value2)) {
return value1.length === value2.length &&
value1.every((val, idx) => isEqual(val, value2[idx]));
}
// Object comparison
if (typeof value2 === 'object') {
return Object.entries(value2).every(([key, val]) =>
value1 && isEqual(value1[key], val)
);
}
return false;
};
// Property matcher
const matchesProperties = item =>
propertyPaths.every(({ parts, value }) =>
isEqual(getNestedValue(item, parts), value)
);
// Input validation
if (!Array.isArray(collection) || typeof properties !== 'object') {
return [];
}
return collection.filter(matchesProperties);
};
// Example usage with nested structures:
/*
const data = [
{
name: 'John',
age: 30,
preferences: {
theme: 'dark',
notifications: { email: true, sms: false }
}
},
{
name: 'Jane',
age: 25,
preferences: {
theme: 'light',
notifications: { email: false, sms: true }
}
}
];
// Find users with specific preferences
const darkThemeUsers = where(data, {
preferences: { theme: 'dark' }
});
// Find users with specific notification settings
const emailSubscribers = where(data, {
preferences: { notifications: { email: true } }
});
*/
if (typeof module !== 'undefined' && module.exports) {
module.exports = where;
}
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