The ECMAScript Technical Committee 39 has put forward a concrete proposal for adding integers to JavaScript:

https://tc39.github.io/proposal-bigint/

The proposal adds a new syntax for integer literals:

42n // This is an integer literal

Implicit conversions to/from numbers and integers and expressions with mixed operands are expressly disallowed:

42n + 1 // Throws TypeError

Type constructors are provided that wrap at specified widths:

• Integer.asUintN(width, Integer): Wrap an Integer between 0 and 2**width-1
• Integer.asIntN(width, Integer): Wrap an Integer between -2**(width-1) and 2**(width-1)-1
• Integer.parseInt(string[, radix]): Analogous to Number.parseInt, to parse an Integer from a String in any base.

Though not stated in the spec, these constructors should theoretically hint to the VM when it's possible to use a native 64-bit integer type instead of a bignum, and could therefore possibly be used by TypeScript to implement int64 and uint64 types in addition to e.g. an integer type of arbitrary precision.

I know people have been asking for integers for quite some time (e.g. #195, #4639), but have been held back by lack of native support of an integer type in JavaScript itself. Now it seems this proposal is stage 2 (scratch that, stage 3!) and has multi-browser vendor backing, so perhaps the prerequisites are finally in place to make integers happen.