Text.Start(), Text.End(), Text.Middle() & Text.Length()

These four functions extract a portion of a text value based on position and length — the basic toolkit for pulling a fixed-format code, a prefix, or a suffix out of a larger text field.

Text.Start(text as text, count as number) as text
Text.End(text as text, count as number) as text
Text.Middle(text as text, start as number, optional count as nullable number) as text
Text.Length(text as text) as number

Text.Start() and Text.End()

Text.Start("INV-2026-0042", 3)
Text.End("INV-2026-0042", 4)

Text.Start(..., 3) -> "INV"
Text.End(..., 4)   -> "0042"

Both count from the respective end of the string — Text.Start from the beginning, Text.End from the end — and simply return fewer characters than requested if the text is shorter than count, rather than erroring.

Text.Middle(): Zero-Indexed Starting Position

Text.Middle("INV-2026-0042", 4, 4)

Position:  0123456789...
Text:      INV-2026-0042
                ^^^^
Text.Middle(..., 4, 4) -> "2026"

The start argument is zero-indexed — position 4 is the 5th character, not the 4th. This is the single most common off-by-one mistake with this function: counting positions starting from 1 (as most people naturally do) produces a result shifted by one character from what was intended.

The count argument is optional — omitting it returns everything from start to the end of the string, equivalent to a variable-length Text.End().

Text.Length(): Combining With a Variable End Position

Text.Middle([Code], 4, Text.Length([Code]) - 4)

This extracts everything from position 4 onward, computing the length dynamically rather than hardcoding it — useful when the meaningful part of a text value has a fixed start but a variable total length across rows.

Common Mistakes

Off-by-One From Treating Position as 1-Indexed

Text.Middle("INV-2026-0042", 5, 4)  -- meant to start at the 5th character

Expected: "2026" (starting at the 5th character, position 4 zero-indexed)
Actually got: "026-"  (started one character too late)

Counting the 5th character as start = 5 instead of start = 4 is the recurring error here — the fix is remembering position 0 is the first character, the same convention List and Table row/column indexing uses elsewhere in M.

Assuming a Fixed Length That Doesn't Hold for Every Row

Text.Start([Code], 3) assumes every value in [Code] has at least a 3-character meaningful prefix — a shorter value doesn't error, it just returns less than expected, which can silently produce wrong-looking results rather than an obvious failure.

Using Text.Middle When Text.End Would Be Simpler

Text.Middle([Code], Text.Length([Code]) - 4, 4)

This correctly extracts the last 4 characters, but Text.End([Code], 4) does the identical thing more directly — worth reaching for the simpler function when the extraction is genuinely anchored to one end of the string, saving the Text.Length arithmetic for cases that actually need a computed middle position.

Next Steps

• M Language
• Text.Split() & Text.Combine()
• M Function Reference