catch clause variablesThanks to work done by @tinganho, TypeScript 2.5 implements a new ECMAScript feature that allows users to omit the variable in catch clauses.\nFor example, when using JSON.parse you may need to wrap calls to the function with a try/catch, but you may not end up using the SyntaxError that gets thrown when input is erroneous.
\ntslet input = \"...\";\ntry {\n JSON.parse(input);\n}\ncatch {\n // ^ Notice that our `catch` clause doesn't declare a variable.\n console.log(\"Invalid JSON given\\n\\n\" + input)\n}
checkJs/@ts-check modeTypeScript 2.5 introduces the ability to assert the type of expressions when using plain JavaScript in your projects.\nThe syntax is an /** @type {...} */ annotation comment followed by a parenthesized expression whose type needs to be re-evaluated.\nFor example:
\ntsvar x = /** @type {SomeType} */ (AnyParenthesizedExpression);
When importing using the Node module resolution strategy in TypeScript 2.5, the compiler will now check whether files originate from “identical” packages.\nIf a file originates from a package with a package.json containing the same name and version fields as a previously encountered package, then TypeScript will redirect itself to the top-most package.\nThis helps resolve problems where two packages might contain identical declarations of classes, but which contain private members that cause them to be structurally incompatible.
As a nice bonus, this can also reduce the memory and runtime footprint of the compiler and language service by avoiding loading .d.ts files from duplicate packages.
--preserveSymlinks compiler flagTypeScript 2.5 brings the preserveSymlinks flag, which parallels the behavior of the --preserve-symlinks flag in Node.js.\nThis flag also exhibits the opposite behavior to Webpack’s resolve.symlinks option (i.e. setting TypeScript’s preserveSymlinks to true parallels setting Webpack’s resolve.symlinks to false, and vice-versa).
In this mode, references to modules and packages (e.g. imports and /// <reference type=\"...\" /> directives) are all resolved relative to the location of the symbolic link file, rather than relative to the path that the symbolic link resolves to.\nFor a more concrete example, we’ll defer to the documentation on the Node.js website.