TypeScript developers migrate JavaScript codebases file by file, raise compiler strictness in controlled steps, and design types that catch real defects rather than merely describing shapes. Companies hire them because turning on strict checking everywhere at once halts delivery, and because a codebase full of implicit any values provides almost none of the safety it appears to.
A codebase can be written in TypeScript and be barely safer than the JavaScript it replaced. Implicit any values, untyped dependencies, and assertions used to silence the compiler all quietly cancel the benefit. Migration is a measurable programme rather than a rename. TechEsperto Solutions runs it that way.
Either strictness is enabled across the whole project on day one, producing thousands of errors and a branch nobody can merge, or files are renamed without types being added, producing a codebase that compiles and checks almost nothing. Both are avoidable. The compiler is designed for gradual adoption, strictness comes as individual flags you enable in sequence, and type coverage is something you can measure and report. TechEsperto Solutions treats migration as an incremental programme with a number attached to it.
Our engagements cover incremental migration from JavaScript, strictness progression programmes, shared type packages spanning frontend and backend, declaration authoring for untyped dependencies, generic utilities, and build and type-check performance work. Most of it is measured improvement on codebases already partly migrated rather than starting from nothing. Where the work extends across a wider system, it is frequently combined with our custom software development practice.
File-by-file conversion with mixed compilation enabled, prioritised by which modules cause most defects. Each batch ships independently, so the codebase never enters an unmergeable state.
Compiler flags enabled one at a time with the resulting errors resolved before the next. Delivered as scheduled increments with type coverage reported at each step.
One definition of your API contracts consumed by both sides, so a backend change surfaces as a frontend compile error rather than a runtime bug found by a customer.
Hand-written declarations for internal or abandoned libraries, and contributions to community type packages where appropriate. Removes the escape hatches that undermine safety at module boundaries.
Reusable generic functions and utility types that remove repetition without becoming unreadable. We keep type-level complexity proportionate, since clever types are expensive to maintain.
Project references, incremental checking, and separating type checking from bundling. Slow feedback loops cause developers to skip checks, which defeats the purpose entirely.
Assessment for this work tests type design judgement rather than syntax knowledge. Anyone can annotate a function. The valuable skills are modelling state so invalid combinations cannot be expressed, aligning runtime validation with static types, authoring declarations for awkward modules, and keeping the compiler fast on a large project. Typed backend work is frequently staffed alongside our Node.js development team.
Configuration that matches your build, with references splitting a large project into independently checkable units. Correct setup is what keeps type checking usable as a codebase grows.
Generic functions that infer correctly at call sites, and conditional types where they genuinely reduce duplication. We stop well short of type-level programming that nobody on your team can modify.
Loading, loaded, and error states as distinct variants rather than one object with optional fields. Makes impossible states unrepresentable, which removes a whole category of defect.
Data crossing a boundary is validated at runtime with schemas that produce the matching static type. Types alone say nothing about what an API actually returned.
Writing declarations for untyped modules and resolving the import resolution problems that appear across mixed module systems. Unglamorous work that removes persistent friction.
Modern bundlers strip types without checking them, so type checking runs separately and must stay fast. Incremental builds and caching configured so feedback arrives in seconds.
Most clients begin with a type audit, because coverage figures usually differ substantially from expectations. Options then include incremental migration projects, strictness progression programmes, shared contract package builds, an embedded developer, and a type health retainer. Our standard arrangements sit in our engagement models. Transparent pricing, an executed NDA, and full intellectual property transfer apply throughout.
We measure type coverage, count implicit any occurrences and assertions, review compiler configuration, check dependency type availability, and time a full type check. The report frequently surprises teams.
Conversion in prioritised batches with mixed compilation, starting with the modules that generate most production defects. Quoted per batch so cost and progress are both visible.
One compiler flag at a time, errors resolved, coverage reported, then the next. Delivered as scheduled increments rather than as a single disruptive change.
A published package defining request and response types consumed by both frontend and backend, with runtime validation aligned to it. Prevents an entire class of integration defect.
One specialist inside your team improving type safety alongside normal feature work. Your developers absorb type design patterns through review rather than through a style guide.
Coverage tracking, dependency type updates, compiler version upgrades, build performance monitoring, and reporting. Type safety erodes gradually unless someone is watching the number.
The method is deliberately unhurried. We measure coverage before changing anything, so improvement is demonstrable. One compiler flag is enabled at a time and its errors resolved fully before the next. Per-directory configuration isolates progress, letting well-typed modules run strictly while older ones catch up. New use of the any escape hatch is banned in review while existing occurrences are tolerated and reduced over time. And the coverage number is reported monthly, which is what keeps the programme alive after the initial enthusiasm fades. Clients working with TechEsperto Solutions get steady measurable progress.
A baseline percentage plus counts of implicit any values and assertions. Without this, nobody can tell whether six months of effort improved anything or merely moved it around.
Null checking, implicit any, function types, and property initialisation each enabled separately. Each produces a manageable error set attributable to one specific cause.
No accumulating suppression comments or deferred work. Completing each step fully is what prevents the programme becoming a permanent partial migration nobody wants to touch.
Strict settings applied to converted areas while legacy directories remain looser. New code is held to the standard immediately even where old code cannot be yet.
Review rejects newly introduced any values and unchecked assertions while tolerating what is already there. Stops the situation worsening while the backlog reduces.
Coverage, error counts, and check duration in a short monthly report. Visible progress is what keeps a long incremental programme funded and prioritised.
Return on typing effort varies enormously by layer. Boundaries between systems, shared packages, and data transformations reward types heavily. Small self-contained scripts barely do. We prioritise accordingly rather than pursuing uniform coverage, which is how a migration delivers value in the first month rather than the ninth. Contract work is frequently delivered alongside our API development practice.
The highest-value place to invest. One shared definition means a changed field breaks the build rather than a customer’s session, and it removes most integration guesswork.
Types propagate to every consumer, so a breaking change surfaces immediately across all of them. Project references keep checking fast as the number of packages grows.
Pipelines where a field renamed upstream silently produces wrong output. Types plus runtime validation at the entry point catch this at the boundary rather than in a report.
Types are your documentation and your compatibility contract. Consumers experience your API through editor completion, which makes declaration quality a product feature.
Deployment definitions and configuration objects where a typo reaches production. Typed configuration turns a runtime failure into a build failure, which is considerably cheaper.
Modules being modified frequently justify conversion first. Stable code nobody touches can stay as it is indefinitely, and converting it rarely repays the effort.
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The entry point is a free type audit. Give us read access and we return a written assessment covering measured type coverage, implicit any and assertion counts, compiler configuration issues, dependency type availability, and full check duration, with a recommended sequence of improvements. Migration phases are quoted individually so approval can happen incrementally. Your team interviews the matched developers, onboarding completes inside a week, and retainers stay optional.
A few days of measurement and a written report with actual numbers. Clients regularly act on it themselves, which is a reasonable outcome and one we are content with.
The starting figures against which all later progress is measured. Establishing this properly is what allows the programme to be reported rather than merely believed.
Each batch or strictness step quoted individually with acceptance criteria covering coverage improvement and passing builds. Budget certainty without committing to the whole programme.
Profiles arrive with relevant migration and type design experience. You assess them against your standards, decline at no cost, and matching continues until the fit is right.
Repository access, build setup, and sprint planning handled immediately so measurable coverage improvement appears inside the first fortnight.
Support begins with coverage tracking and dependency type updates, which is where erosion happens, expanding into compiler upgrades and build performance monitoring.
Our work and story have been picked up by news outlets and databases worldwide.
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Type audits are free. Migration batches and strictness steps are quoted individually at fixed prices, which makes budgeting incremental and predictable. Shared contract packages are a defined short engagement. Embedded developers are quoted monthly. There is no third-party consumption cost in this work.
A small codebase reaches full conversion in three to six weeks. Medium applications typically run three to six months of incremental work alongside normal delivery, which is the recommended pace. Individual strictness steps are usually one to three weeks each. Untyped third-party dependencies are the most common cause of delay.
One senior developer is usually correct, since type design benefits from consistency and suffers from several people establishing different conventions. Larger codebases occasionally justify two working in separate areas with an agreed convention document.
Our developers join your repository and review process. Weekly reporting covers coverage figures, error counts, and check duration, which makes progress objective. Type conventions are documented as they are agreed rather than left implicit.
Read access for the audit, then contributor access if we proceed. A mutual NDA is signed first. We work in your repository rather than copying code elsewhere, and nothing from a client engagement is reused on another project.
We staff for at least four hours of daily overlap with your business day across North American, UK, European, and Australian schedules. Reviews and pairing sessions sit inside that window.
Coverage tracking is the main one, because type safety erodes quietly as pressure to ship increases. Retainers cover coverage reporting, dependency type updates, compiler version upgrades, and build performance monitoring so a completed migration stays completed.
Full TypeScript is right for applications under active development by more than one or two people, where the compile step is acceptable and safety compounds over time. JSDoc annotations with type checking enabled are a genuinely good middle option for libraries and codebases wanting no build step, since you get most of the checking with plain JavaScript files, at the cost of clumsier syntax for complex types. Staying on untyped JavaScript is defensible for small scripts, short-lived code, and single-maintainer projects where the overhead would exceed the benefit. We assess your team size, change frequency, and defect patterns rather than assuming migration is always correct.
Tell us what you’re building. Our team will get back to you within one business day with a clear, no-obligation plan.
