dropWhile()

dropWhile<T>(array, predicate): T[]

Creates a slice of array excluding elements dropped from the beginning. Elements are dropped until predicate returns falsey.

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Type Parameters

T: T

The type of elements in the array.

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Parameters

array: readonly T[]

The source array to query.

predicate: (value, index, array) => boolean

The function invoked per iteration.

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Returns: T[]

A new array with the leading elements dropped.

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Since

2.0.0

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Performance

O(n) — single forward pass with final slice.

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Also known as

dropWhile (Lodash, es-toolkit, Remeda, Ramda, Effect, Modern Dash) · ❌ (Radashi, Antfu)

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Example

dropWhile([1, 2, 3, 4, 5], (v) => v < 3);
// => [3, 4, 5]

dropWhile(
  [{ name: 'Alice', active: false }, { name: 'Bob', active: true }],
  (u) => !u.active
);
// => [{ name: 'Bob', active: true }]

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How it works?

Drops elements from the beginning while the predicate returns true. Stops at first falsy result.

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Use Cases

Skip leading falsy or invalid entries 📌

Drop elements from the start of an array while they fail a validation check. Perfect for processing data streams, logs, or inputs that may have leading garbage values.

#skip#leading#falsy#invalid#validation#cleanup

const logs = ["", "", "INFO: Started", "DEBUG: Loaded", "ERROR: Failed"];

const meaningfulLogs = dropWhile(logs, (log) => log === "");
// => ["INFO: Started", "DEBUG: Loaded", "ERROR: Failed"]

Skip sorted elements below a threshold

Drop leading elements from a sorted array until a condition is met. Perfect for time-series data, paginated results, or filtering out outdated entries.

#skip#sorted#threshold#condition#timeseries#filtering

const transactions = [
  { date: new Date("2024-01-15"), amount: 100 },
  { date: new Date("2024-06-20"), amount: 250 },
  { date: new Date("2025-01-10"), amount: 75 },
  { date: new Date("2025-03-05"), amount: 300 },
];

const thisYearTransactions = dropWhile(
  transactions,
  (t) => t.date.getFullYear() < 2025
);
// => [{ date: 2025-01-10, amount: 75 }, { date: 2025-03-05, amount: 300 }]

Skip header rows in structured data

Drop leading metadata or header rows before processing actual content. Perfect for parsing CSV files, API responses with metadata, or documents with preambles.

#skip#header#metadata#CSV#parsing#structured

const csvRows = [
  { type: "header", value: "Name,Age,City" },
  { type: "header", value: "---,---,---" },
  { type: "data", value: "Alice,25,Paris" },
  { type: "data", value: "Bob,30,Lyon" },
];

const dataRows = dropWhile(csvRows, (row) => row.type === "header");
// => [{ type: "data", value: "Alice,25,Paris" }, { type: "data", value: "Bob,30,Lyon" }]