TypeScript¶

Typed superset of JavaScript for large-scale applications

Overview¶

TypeScript adds static typing to JavaScript, making it easier to build and maintain large applications. With run, you can execute TypeScript code using Deno.

Language Aliases¶

run typescript "console.log('Hello')"
run ts "console.log('Hello')"
run ts-node "console.log('Hello')"
run deno "console.log('Hello')"
# Output: Hello (x4)

Important: Deno Module Specifiers¶

run uses Deno for TypeScript execution. Deno requires explicit module specifiers and does not accept bare Node builtin names like 'fs'.

Use the node: prefix for Node builtins (for example import fs from 'node:fs'). Also prefer a quoted here-doc for multi-line snippets to avoid shell interpolation/globbing issues.

Correct - Using node: prefix (here-doc recommended)¶

cat <<'EOF' | run typescript
import fs from "node:fs";
console.log('[TypeScript] hello');
EOF
# Output: [TypeScript] hello

Safe inline (zsh)¶

run --lang typescript --code $'import fs from "node:fs";\nconsole.log("[TypeScript] hello");\n'
# Output: [TypeScript] hello

Basic TypeScript Example¶

cat <<'EOF' | run typescript
const greet = (name: string): string => {
  return `Hello, ${name}!`;
};
console.log(greet('World'));
EOF
# Output: Hello, World!

Multi-line Code¶

# RECOMMENDED
run typescript << 'EOF'
interface User {
  name: string;
  age: number;
}
const users: User[] = [{name: 'Alice', age: 30}];
console.log(users);
EOF

# OK: Single-line
run ts "const x: number[] = [1,2,3]; console.log(x.map(n => n*2));"

REPL Behavior¶

TypeScript's REPL is STATEFUL when using ts-node.