Mimimal code to compile TypeScript string (from https://github.com/Microsoft/TypeScript/wiki/Using-the-Compiler-API)

gistfile1.ts

/// <reference path="typings/node/node.d.ts" />
/// <reference path="typings/typescript/typescript.d.ts" />

import ts = require("typescript");
import fs = require("fs");
import path = require("path");

function transform(contents: string, libSource: string, compilerOptions: ts.CompilerOptions = {}) {
    // Generated outputs
    var outputs = [];
    // Create a compilerHost object to allow the compiler to read and write files
    var compilerHost = {
        getSourceFile: function (filename, languageVersion) {
            if (filename === "file.ts")
                return ts.createSourceFile(filename, contents, compilerOptions.target, "0");
            if (filename === "lib.d.ts")
                return ts.createSourceFile(filename, libSource, compilerOptions.target, "0");
            return undefined;
        },
        writeFile: function (name, text, writeByteOrderMark) {
            outputs.push({ name: name, text: text, writeByteOrderMark: writeByteOrderMark });
        },
        getDefaultLibFilename: function () { return "lib.d.ts"; },
        useCaseSensitiveFileNames: function () { return false; },
        getCanonicalFileName: function (filename) { return filename; },
        getCurrentDirectory: function () { return ""; },
        getNewLine: function () { return "\n"; }
    };
    // Create a program from inputs
    var program = ts.createProgram(["file.ts"], compilerOptions, compilerHost);
    // Query for early errors
    var errors = program.getDiagnostics();
    // Do not generate code in the presence of early errors
    if (!errors.length) {
        // Type check and get semantic errors
        var checker = program.getTypeChecker(true);
        errors = checker.getDiagnostics();
        // Generate output
        checker.emitFiles();
    }
    return {
        outputs: outputs,
        errors: errors.map(function (e) { return e.file.filename + "(" + e.file.getLineAndCharacterFromPosition(e.start).line + "): " + e.messageText; })
    };
}

// Calling our transform function using a simple TypeScript variable declarations, 
// and loading the default library like:
var source = "var x: number  = 'string'";
var libSource = fs.readFileSync(path.join(path.dirname(require.resolve('typescript')), 'lib.d.ts')).toString();
var result = transform(source, libSource);

console.log(JSON.stringify(result));