TypeScript 2.3 RC 変更点

function* f() {
    yield 1;
    yield* [2, 3];
}

const array = [1, 2, 3];
for (const v of array) {
    console.log(v);
}

const map = new Map<string, string>();
map.set("a", "b");
for (const v of map) {
    console.log(v);
}

const obj = {
    [Symbol.iterator]() {
        return g();

        function* g() {
            yield 1;
            yield* [2, 3];
        }
    },
};
for (const v of obj) {
    console.log(v);
}
const [a1, a2, a3] = obj;

// Node.js v7.8.0 だと Symbol.asyncIterator は存在してない…
(Symbol as any).asyncIterator = Symbol.asyncIterator || Symbol.for("Symbol.asyncIterator");

function sleep(milliseconds: number) {
    return new Promise(resolve => setTimeout(resolve, milliseconds));
}

async function* getItemsReallySlowly<T>(items: Iterable<T>) {
    for (const item of items) {
        await sleep(500);
        yield item;
    }
}

async function speakLikeSloth(items: string[]) {
    for await (const item of getItemsReallySlowly(items)) {
        console.log(item);
    }
}

speakLikeSloth("never gonna give you up never gonna let you down".split(" "))

class Container<T = string> {
    data?: T;
}

const objA = new Container();
// index.ts(54,1): error TS2322: Type '1' is not assignable to type 'string | undefined'.
objA.data = 1;

const objB = new Container<number>();
objB.data = 1;

const obj = {
    name: "maya",
    greeting() {
        return `Hello, ${this.name}`;
    },
    compileError() {
        // error TS2339: Property 'notExists' does not exist on
        //   type '{ name: string; greeting(): string; compileError(): any; }'.
        return `Hello, ${this.notExists}`;
    },
};
console.log(obj.greeting());

class Sample {
    name: string;
    hello() {
        console.log(`Hello, ${this.name || "world"}`);
    }
}

Sample.prototype.hello = function () {
    // error TS2339: Property 'notExists' does not exist on type 'Sample'.
    console.log(`Hi, ${this.notExists || "world"}`);
};

interface A {
    name: string;
}
interface B {
    hello(): void;
}

// objの型はBであり、obj内でのthisの型はAと明示的に指定する
const obj: B & ThisType<A> = {
    hello() {
        console.log(`Hello, ${this.name}`);
        // error TS2339: Property 'notExists' does not exist on type 'A'.
        console.log(`Hello, ${this.notExists}`);
    },
};
obj.hello();

{
  "compilerOptions": {
    /* Basic Options */                       
    "target": "es5",                          /* Specify ECMAScript target version: 'ES3' (default), 'ES5', 'ES2015', 'ES2016', 'ES2017', or 'ESNEXT'. */
    "module": "commonjs",                     /* Specify module code generation: 'commonjs', 'amd', 'system', 'umd' or 'es2015'. */
    // "lib": [],                             /* Specify library files to be included in the compilation:  */
    // "allowJs": true,                       /* Allow javascript files to be compiled. */
    // "checkJs": true,                       /* Report errors in .js files. */
    // "jsx": "preserve",                     /* Specify JSX code generation: 'preserve', 'react-native', or 'react'. */
    // "declaration": true,                   /* Generates corresponding '.d.ts' file. */
    // "sourceMap": true,                     /* Generates corresponding '.map' file. */
    // "outFile": "./",                       /* Concatenate and emit output to single file. */
    // "outDir": "./",                        /* Redirect output structure to the directory. */
    // "rootDir": "./",                       /* Specify the root directory of input files. Use to control the output directory structure with --outDir. */
    // "removeComments": true,                /* Do not emit comments to output. */
    // "noEmit": true,                        /* Do not emit outputs. */
    // "importHelpers": true,                 /* Import emit helpers from 'tslib'. */
    // "downlevelIteration": true,            /* Provide full support for iterables in 'for-of', spread, and destructuring when targeting 'ES5' or 'ES3'. */
    // "isolatedModules": true,               /* Transpile each file as a separate module (similar to 'ts.transpileModule'). */

    /* Strict Type-Checking Options */        
    "strict": true                            /* Enable all strict type-checking options. */
    // "noImplicitAny": true,                 /* Raise error on expressions and declarations with an implied 'any' type. */
    // "strictNullChecks": true,              /* Enable strict null checks. */
    // "noImplicitThis": true,                /* Raise error on 'this' expressions with an implied 'any' type. */
    // "alwaysStrict": true,                  /* Parse in strict mode and emit "use strict" for each source file. */

    /* Additional Checks */                   
    // "noUnusedLocals": true,                /* Report errors on unused locals. */
    // "noUnusedParameters": true,            /* Report errors on unused parameters. */
    // "noImplicitReturns": true,             /* Report error when not all code paths in function return a value. */
    // "noFallthroughCasesInSwitch": true,    /* Report errors for fallthrough cases in switch statement. */

    /* Module Resolution Options */           
    // "moduleResolution": "node",            /* Specify module resolution strategy: 'node' (Node.js) or 'classic' (TypeScript pre-1.6). */
    // "baseUrl": "./",                       /* Base directory to resolve non-absolute module names. */
    // "paths": {},                           /* A series of entries which re-map imports to lookup locations relative to the 'baseUrl'. */
    // "rootDirs": [],                        /* List of root folders whose combined content represents the structure of the project at runtime. */
    // "typeRoots": [],                       /* List of folders to include type definitions from. */
    // "types": [],                           /* Type declaration files to be included in compilation. */
    // "allowSyntheticDefaultImports": true,  /* Allow default imports from modules with no default export. This does not affect code emit, just typechecking. */

    /* Source Map Options */                  
    // "sourceRoot": "./",                    /* Specify the location where debugger should locate TypeScript files instead of source locations. */
    // "mapRoot": "./",                       /* Specify the location where debugger should locate map files instead of generated locations. */
    // "inlineSourceMap": true,               /* Emit a single file with source maps instead of having a separate file. */
    // "inlineSources": true,                 /* Emit the source alongside the sourcemaps within a single file; requires '--inlineSourceMap' or '--sourceMap' to be set. */

    /* Experimental Options */                
    // "experimentalDecorators": true,        /* Enables experimental support for ES7 decorators. */
    // "emitDecoratorMetadata": true,         /* Enables experimental support for emitting type metadata for decorators. */
  }
}