tc39/proposal-pipeline-operator
Proposal Pipeline Operator
This is an ECMAScript proposal that introduces a pipeline operator for JavaScript, enabling left-to-right expression chaining with a dedicated placeholder token to reference the previous step's value. The proposal defines a syntax-only transformation that desugars to standard JavaScript, requiring no new runtime support or engine primitives.
The pipeline operator allows chaining operations sequentially, passing each result to the next step in natural reading order. It includes a null-safe variant that short-circuits on nullish values, returning them unchanged and skipping remaining steps. Each pipeline step evaluates in the same lexical scope as the surrounding code, preserving variable access without closure overhead.
The proposal also covers binding values in control flow statements, such as conditions in if statements, caught errors in catch blocks, and iterated values in for-of loops. This enables expression-oriented programming patterns where operations compose without intermediate variables or function wrappers.
