# Drop While

Drop items from array while predicate is true using lodash _.dropWhile

> Canonical page: https://elysiatools.com/en/tools/drop-while

- **Category:** Data Processing

- **Keywords:** array, drop, while, predicate, conditional, filter, lodash

## Overview

This tool removes elements from the beginning of an array until the predicate returns false for the first time.

**Features:**
- Multiple predicate types for flexible filtering
- Support for numeric and string comparisons
- Works with arrays of any data type
- Uses lodash's _.dropWhile for reliable operation

**Example:**
Input: `[1, 2, 3, 4, 5]`
Predicate: Less than 3
Output: `[3, 4, 5]` (drops 1 and 2 because they are < 3)

**Predicate Types:**
- **less-than**: Drop while value < n
- **greater-than**: Drop while value > n
- **equals**: Drop while value === n
- **not-equals**: Drop while value !== n
- **string-contains**: Drop while string contains substring
- **string-starts-with**: Drop while string starts with prefix
- **string-ends-with**: Drop while string ends with suffix
- **is-nullish**: Drop while value is null/undefined
- **is-truthy**: Drop while value is truthy
- **is-falsey**: Drop while value is falsey

## Inputs

- **Array** (textarea): Enter a JSON array
- **Predicate Type** (select): Select the condition for dropping elements
- **Compare Value** (text): Value to compare against (required for most predicates)

## When to use

- When you need to trim leading elements from an array that do not meet a specific numeric or string criteria.
- When processing sorted or ordered data to skip initial entries until a threshold is reached.
- When cleaning data by removing null, undefined, or other falsy values from the start of an array.

## How it works

- Input your array in JSON format into the provided textarea.
- Select a predicate type from the dropdown, such as 'less-than' or 'string-contains'.
- Provide a compare value if required by the predicate type (e.g., a number or string).
- The tool processes the array, dropping elements from the start until the predicate returns false, and outputs the remaining array.

## Use cases

- Removing leading zeros or low values from a sorted list of numbers in data analysis.
- Skipping initial debug or info log entries until an error message appears in log processing.
- Filtering out empty strings or null values from the start of a text array for data cleaning.

## Frequently asked questions

### What is a predicate in this tool?

A predicate is a condition used to evaluate each element, such as checking if a value is less than a number or if a string contains a substring.

### Can I use this tool with arrays of mixed data types?

Yes, it works with arrays of any data type, but predicates like 'less-than' are designed for numeric comparisons, while others like 'string-contains' are for strings.

### What happens if no elements are dropped?

If the predicate is false for the first element, no elements are dropped, and the original array is returned unchanged.

### Is the original array modified?

No, the tool creates a new array with elements dropped, leaving the original input array intact.

### How do I specify the compare value for string predicates?

Enter the string value in the 'Compare Value' field, such as 'abc' for 'string-contains' or a prefix for 'string-starts-with'.

## Related tools

- [Compact Array](https://elysiatools.com/en/tools/compact-array): Remove falsey values from array using lodash _.compact
- [Drop Items](https://elysiatools.com/en/tools/drop-items): Drop first N items from array using lodash _.drop
- [Drop Right Items](https://elysiatools.com/en/tools/drop-right-items): Drop last N items from array using lodash _.dropRight
- [Fill Array](https://elysiatools.com/en/tools/fill-array): Fill array with value from start to end index using lodash _.fill
- [From Pairs](https://elysiatools.com/en/tools/from-pairs): Convert array of key-value pairs to object using lodash _.fromPairs
- [Last Item](https://elysiatools.com/en/tools/last-item): Get the last item from an array using lodash _.last
- [Pull Values](https://elysiatools.com/en/tools/pull-values): Remove specific values from an array using lodash _.pull
- [Sorted Unique](https://elysiatools.com/en/tools/sorted-unique): Remove duplicates from a sorted array using lodash _.sortedUniq

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