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Module Basics
Minimal module Function declaration Function export Function import Function parameters Function results Local variables Global variables Mutable globals Start function
Numeric Instructions
i32.const i64.const f32.const f64.const i32.add i32.sub i32.mul i32.div_s f64.add Numeric conversion
Control Flow
block loop br br_if if then else select return call call_indirect unreachable
Memory
Memory declaration Memory export Data segment i32.load i32.store load8_u store8 memory.size memory.grow Memory offset
Tables & References
Table declaration funcref elem segment ref.null ref.func table.get table.set table.size table.grow Indirect function table
Advanced Numeric
i32.and i32.or i32.xor i32.shl i32.shr_s i32.rotl i32.eqz Comparison instructions Saturating truncation reinterpret instructions
JS Interop Concepts
Import JavaScript function Export function to JavaScript Shared linear memory concept Passing integers Passing strings via memory Reading UTF-8 from memory Writing results to memory Memory buffer refresh Host error boundary InstantiateStreaming pattern
Advanced Features
Multi-value results Bulk memory memory.copy memory.fill table.copy SIMD v128.const SIMD i32x4.add Exception tags concept Threads atomic load Threads atomic store Component model concept
WebAssembly Complete Course / JS Interop Concepts

Reading UTF-8 from memory

Learn Reading UTF-8 from memory in WebAssembly through the exact construct, a dedicated example, a boundary case, and a mastery check.

12 min read • Advanced

Reading UTF-8 from memory is an atomic WebAssembly lesson inside JS Interop Concepts. The example uses the specific syntax, command, API, instruction, or language rule named by this lesson.

Study the construct itself, then change one relevant input and predict the result before running it. That keeps this lesson focused on Reading UTF-8 from memory rather than on generic WebAssembly syntax.

Topic-specific example

webassembly-07-06.wat
wat Try It Live 
const bytes = new Uint8Array(instance.exports.memory.buffer, ptr, len);
const text = new TextDecoder().decode(bytes);
Edge case / engineering note

For Reading UTF-8 from memory, check operand/result types and trap conditions. WebAssembly validation is strict even when the surrounding host code is permissive.

Content source & attribution
Original Syntaxis Content · Original Syntaxis Content

Lesson quizzes

Reading UTF-8 from memory Mastery Check →
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