typebox/docs/values/cast.md

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Cast

Use the Cast function to upcast a value into a target type. This function will retain as much information as possible from the original value. The Cast function is intended to be used in data migration scenarios where existing values need to be upgraded to match a modified type.

const T = Type.Object(
  { x: Type.Number(), y: Type.Number() },
  { additionalProperties: false }
);

const X = Value.Cast(T, null); // const X = { x: 0, y: 0 }

const Y = Value.Cast(T, { x: 1 }); // const Y = { x: 1, y: 0 }

const Z = Value.Cast(T, { x: 1, y: 2, z: 3 }); // const Z = { x: 1, y: 2 }

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