1Use in TypeScript {#flatbuffers_guide_use_typescript}
2=================
3
4## Before you get started
5
6Before diving into the FlatBuffers usage in TypeScript, it should be noted that
7the [Tutorial](@ref flatbuffers_guide_tutorial) page has a complete guide to
8general FlatBuffers usage in all of the supported languages
9(including TypeScript). This page is specifically designed to cover the nuances
10of FlatBuffers usage in TypeScript.
11
12You should also have read the [Building](@ref flatbuffers_guide_building)
13documentation to build `flatc` and should be familiar with
14[Using the schema compiler](@ref flatbuffers_guide_using_schema_compiler) and
15[Writing a schema](@ref flatbuffers_guide_writing_schema).
16
17## FlatBuffers TypeScript library code location
18
19The code for the FlatBuffers TypeScript library can be found at
20https://www.npmjs.com/package/flatbuffers.
21
22## Testing the FlatBuffers TypeScript library
23
24To run the tests, use the [TypeScriptTest.py](https://github.com/google/
25flatbuffers/blob/master/tests/TypeScriptTest.py) Python3 script.
26
27*Note: The TypeScript test file requires [Node.js](https://nodejs.org/en/).*
28
29## Using the FlatBuffers TypeScript library
30
31*Note: See [Tutorial](@ref flatbuffers_guide_tutorial) for a more in-depth
32example of how to use FlatBuffers in TypeScript.*
33
34FlatBuffers supports both reading and writing FlatBuffers in TypeScript.
35
36To use FlatBuffers in your own code, first generate TypeScript classes from your
37schema with the `--ts` option to `flatc`. Then you can include both FlatBuffers
38and the generated code to read or write a FlatBuffer.
39
40For example, here is how you would read a FlatBuffer binary file in TypeScript:
41First, include the library and generated code. Then read the file into an
42`Uint8Array`. Make a `flatbuffers.ByteBuffer` out of the `Uint8Array`, and pass
43the ByteBuffer to the `getRootAsMonster` function.
44
45~~~{.ts}
46 import * as flatbuffers from 'flatbuffers';
47
48 import { MyGame } from './monster_generated';
49
50 let data = new Uint8Array(fs.readFileSync('monster.dat'));
51 let buf = new flatbuffers.ByteBuffer(data);
52
53 let monster = MyGame.Example.Monster.getRootAsMonster(buf);
54~~~
55
56Now you can access values like this:
57
58~~~{.ts}
59 let hp = monster.hp();
60 let pos = monster.pos();
61~~~
62
63## Object based API
64
65FlatBuffers is all about memory efficiency, which is why its base API is written
66around using as little as possible of it. This does make the API clumsier
67(requiring pre-order construction of all data, and making mutation harder).
68
69For times when efficiency is less important a more convenient object based API
70can be used (through `--gen-object-api`) that is able to unpack & pack a
71FlatBuffer into objects and standard TS types.
72
73To use:
74
75~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.ts}
76 // Autogenerated class from table Monster.
77 let monsterobj = new MonsterT();
78
79 // Deserialize from buffer into object.
80 Monster.getRootAsMonster(flatbuffer).unpackTo(monsterobj);
81 // or
82 let monsterobj = Monster.getRootAsMonster(flatbuffer).unpack();
83
84 // Update object directly like a regular TS class instance.
85 console.log(monsterobj.name);
86 monsterobj.name = "Bob";
87
88 // Serialize into new flatbuffer.
89 let fbb = new flatbuffers.Builder(1);
90 Monster.finishMonsterBuffer(fbb, monsterobj.pack(fbb));
91~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
92
93## Text parsing FlatBuffers in TypeScript
94
95There currently is no support for parsing text (Schema's and JSON) directly
96from TypeScript.
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