A throw expression is an expression form that raises an exception from within an expression context. As a proposed JavaScript feature, it treats throwing more like a value-producing artifact than a statement restricted to a block. section 7.4.2 section 1.1
Its practical value is composability: code can raise an exception while initializing a parameter or evaluating a compact expression, without creating a separate function or block solely to contain throw. section 7.4.2
Default-parameter validation
function proofOfWork(block = throw new Error('Provide a non-null block object!')) { ... } section 7.4.2
The proposal extends throwing to expression-oriented locations such as:
- Default-parameter initialization, as in proofOfWork. section 7.4.2
- One-line arrow functions, conditionals, switch statements, and logical-operator evaluation. section 7.4.2
Without throw expressions, equivalent behavior requires wrapping the exception in a function or moving it into a block where throw is allowed. The feature therefore shortens error-handling code, but remains proposal-based and may require explicit enablement. section 7.4.2 section 1.1
