Essential Go Maps  Suggest an edit

Get map size (number of map entries)

The built-in function len returns the number of elements in a map

m := map[string]int{}
len(m) // 0

m["foo"] = 1
len(m) // 1

If a variable points to a nil map, then len returns 0.

var m map[string]int
len(m) // 0

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