title: What is the return type of resolve and reject function of a Promise?
body: <p>I am trying to find the return type of resolve and reject function of a Promise I am creating with typescript, so that tslint does not complain based on the typedef rules.</p>
  
  <p>Here is the code :</p>
  
  <p>promises.ts</p>
  
  <pre><code>const promise: Promise&lt;number&gt; = new Promise((resolve, reject): void =&gt; {
      //the resolve / reject functions control the fate of the promise
      resolve(123);
  });
  
  //The promise fate can be subscribed to using .then (if resolved) or .catch (if rejected)
  promise.then((res) =&gt; {
      console.log('I get called:', res === 123);      //I get called: true
  });
  </code></pre>
  
  <hr>
  
  <p>tslint.json</p>
  
  <pre><code>{
      "defaultSeverity": "error",
      "extends": [
          "tslint:recommended"
      ],
      "jsRules": {},
      "rules": {
          "eofline": false,
          "no-console": false,
          "no-consecutive-blank-lines": false,
          "comment-format": false,
          "no-trailing-whitespace": false,
          "quotemark": false,
          "typedef": [true, "call-signature", "arrow-call-signature", "parameter", "arrow-parameter", "property-declaration", "variable-declaration", "member-variable-declaration"],
          "typedef-whitespace": false,
          "whitespace": false
      },
      "rulesDirectory": []
  }
  </code></pre>
  
  <hr>
  
  <p>tsconfig.json</p>
  
  <pre><code>{
    "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": "./build/",                        /* 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. */
      "lib": [
        "dom",
        "es5",
        "es2015.promise"
      ]
    }
  }
  </code></pre>
  
  <hr>
  
  <p>package.json</p>
  
  <pre><code>{
    "name": "TypescriptProject5",
    "version": "1.0.0",
    "description": "",
    "main": "index.js",
    "scripts": {
      "start": "webpack-dev-server",
      "build": "webpack --watch",
      "test": "echo \"Error: no test specified\" &amp;&amp; exit 1"
    },
    "keywords": [],
    "author": "",
    "license": "ISC",
    "devDependencies": {
      "ts-loader": "^2.1.0",
      "tslint": "^5.4.2",
      "typescript": "^2.3.4",
      "webpack": "^2.6.1",
      "webpack-dev-server": "^2.4.5",
      "write-file-webpack-plugin": "^4.0.2"
    },
    "dependencies": {
      "es6-promise": "^4.1.0"
    }
  }
  </code></pre>
  
  <p>Right now tslint complains about resolve, reject and res (expected arrow parameter to have a typedef)</p>
  
  <p>Update #2 : This code does not give me any tslint or TS errors</p>
  
  <pre><code>const promise: Promise&lt;number&gt; = new Promise((resolve: (value?: {} | PromiseLike&lt;{}&gt; | undefined) =&gt; void, reject: (reason?: any) =&gt; void): void =&gt; {
      //the resolve / reject functions control the fate of the promise
      resolve(123);
  });
  
  //The promise fate can be subscribed to using .then (if resolved) or .catch (if rejected)
  promise.then((res: number) =&gt; {
      console.log('I get called:', res === 123);      //I get called: true
  });
  </code></pre>