Runtime Schema Detection

Detect Standard Schema values at runtime with isStandardSchema.

isStandardSchema detects Standard Schema values at runtime — a type guard that checks whether a value implements the Standard Schema interface.

Signature

function isStandardSchema(value?: unknown): value is StandardSchemaV1;

Parameters

Returns

boolean — true if the value is a Standard Schema, otherwise false. When it returns true, TypeScript narrows value to StandardSchemaV1.

Behavior

The guard returns true when the value is:

• not null or undefined, and
• an object or a function, and
• has a ~standard property.

It checks for the presence of the ~standard property only; it does not verify that ~standard.validate is callable. If a malformed value passes the guard, the validation helpers throw a TypeError at call time.

Basic Usage

import { isStandardSchema } from "@zap-studio/validation";

if (isStandardSchema(schemaLike)) {
  // schemaLike is now typed as StandardSchemaV1
}

Guard Before Validation

Use the guard when schema values are dynamic, external, or typed as unknown — for example when they come from plugins, shared registries, or configuration.

import { isStandardSchema, standardValidate } from "@zap-studio/validation";

export async function validateIfPossible(input: unknown, schemaLike: unknown) {
  if (!isStandardSchema(schemaLike)) {
    return { ok: false as const, reason: "not-a-schema" as const };
  }

  const result = await standardValidate(input, schemaLike);

  if (result.issues) {
    return {
      ok: false as const,
      reason: "invalid-input" as const,
      issues: result.issues,
    };
  }

  return { ok: true as const, value: result.value };
}

When to Use It

• schema objects come from external modules or user configuration
• your API accepts flexible unknown inputs
• you build framework or package boundaries and want explicit runtime checks

If schema values are always strongly typed as StandardSchemaV1, you usually do not need this guard.

See Also

• Async Validation