Format M data as JSON

json.m

let
    ByteToHex = (i as number) as text =>
        let
            chars = "0123456789abcdef",
            low = Text.Range(chars, Number.Mod(i, 16), 1),
            high = Text.Range(chars, Number.RoundDown(i / 16), 1)
        in high & low,
    Json.EscapeChar = (text as text) as text =>
        if text = """" or text = "\" or text = "/" then "\" & text
        else if Character.ToNumber(text) < 32 then "\u00" & ByteToHex(Character.ToNumber(text))
        else text,
    Json.FormatText = (text as text) as text => """" & Text.Combine(List.Transform(Text.ToList(text), Json.EscapeChar)) & """",
    Json.FormatLogical = (value as logical) as text => if value then "true" else "false",
    Number.IsNumber = (value as number) as logical => not Number.IsNaN(value) and value <> Number.PositiveInfinity and value <> Number.NegativeInfinity,
    Json.FormatNumber = (value as number) as text => if Number.IsNumber(value) then Text.From(value, "") else error Error.Record("Expression.Error", "Not a number", value),
    Json.FormatList = (value as list) as text => "[" & Text.Combine(List.Transform(value, Json.Format), ",") & "]",
    Json.FormatPair = (key as text, record as record) as text => Json.FormatText(key) & ":" & Json.Format(Record.Field(record, key)),
    Json.FormatRecord = (value as record) as text => "{" & Text.Combine(List.Transform(Record.FieldNames(value), (key) => Json.FormatPair(key, value)), ",") & "}",
    Json.Format = (value) as text =>
        if value = null then "null"
        else if value is text then Json.FormatText(value)
        else if value is logical then Json.FormatLogical(value)
        else if value is number then Json.FormatNumber(value)
        else if value is list then Json.FormatList(value)
        else if value is record then Json.FormatRecord(value)
        else if value is table then Json.FormatList(Table.ToRecords(value))
        else error Error.Record("Expression.Error", "Unsupported value", value)
in
    Json.Format(Table.FromRows({{"A", "B", "C"}, {1, 2, 3}}))

Now that Json.FromValue is in the standard library, this is probably less interesting.