Getting started

samber/lo is a Lodash-style utility library for Go 1.18+ that leverages generics to provide type-safe helper functions. The library is organized into several packages, each serving different use cases.

🚀 Install

go get -u github.com/samber/lo@v1

🧢 Core Package (lo)

The main package provides immutable utility functions for slices, maps, strings, math operations, and more. It's the core of the library with over 300+ functions.

import "github.com/samber/lo"

// Example: Map a slice of numbers to their squares
numbers := []int{1, 2, 3, 4, 5}
squared := lo.Map(numbers, func(x int, _ int) int {
    return x * x
})
// Result: [1, 4, 9, 16, 25]

🔄 Iter Package (lo/it)

The it package provides Go 1.23+ sequence helpers with lazy evaluation, offering over 100 functions for efficient iteration without buffering.

// Future usage (Go 1.23+)
import (
    "iter"
    loi "github.com/samber/lo/it"
)

seqIn := iter.Range(0, 1000)

// Lazy iteration without buffering
seqOut := loi.Filter(seqIn, func(x int) bool {
    return x%2 == 0
})

👣 Mutable Package (lo/mutable)

The mutable package provides in-place operations that modify collections directly, useful for performance-critical scenarios.

import lom "github.com/samber/lo/mutable"

// Filter in-place (modifies the original slice)
numbers := []int{1, 2, 3, 4, 5}
lom.Filter(&numbers, func(x int) bool {
    return x%2 == 0
})
// Result: [2, 4]

🏎️ Parallel Package (lo/parallel)

The parallel package enables concurrent processing of collections with built-in worker pools, perfect for CPU-intensive operations.

import lop "github.com/samber/lo/parallel"

// Process items concurrently (4 workers by default)
results := lop.Map(numbers, 4, func(x int) int {
    // Some expensive operation
    return expensiveOperation(x)
})

✅ Key Benefits

• Type-safe with generics
• Immutable by default (main package)
• Performance optimized with parallel and mutable variants
• Comprehensive with 500+ utility functions
• Lazy evaluation with iter std package (Go >= 1.23)
• Minimal dependencies zero dependencies outside the Go standard library

👀 Next Steps

• Check the Go documentation for complete API reference
• Explore examples in the repository
• Choose the right sub-package for your use case