Collecting all errors with Ajv

How it works

1. Create two instances. Options go into the constructor. This example builds one instance with no options and one with { allErrors: true }, then compiles the same schema with both. [1]
2. Compare the error lists. The same invalid object is validated twice. In the output, the default instance reports a single error while the allErrors instance lists the empty name, the negative age, the wrong email type and the missing role. [2]
3. Print each error. Each error object carries the reason it failed. The loop passes errors one at a time to ajv.errorsText() to print one line per problem. [1]

Run and edit it

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import Ajv from "ajv"

const schema = {
  type: "object",
  properties: {
    name: { type: "string", minLength: 1 },
    age: { type: "integer", minimum: 0 },
    email: { type: "string" },
  },
  required: ["name", "age", "email", "role"],
}

const data = { name: "", age: -3, email: 42 }
console.log("data:", JSON.stringify(data))

const instances = [
  ["default", new Ajv()],
  ["allErrors", new Ajv({ allErrors: true })],
]

for (const [label, ajv] of instances) {
  const validate = ajv.compile(schema)
  validate(data)
  console.log("")
  console.log(`${label}: ${validate.errors.length} error(s)`)
  for (const err of validate.errors) {
    console.log("  -", ajv.errorsText([err]))
  }
}

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Fix one field in data at a time and watch the allErrors list shrink while the default count stays at one until everything passes. Code written by AgentGid [1].

Checked Oct 12, 2026: it starts without errors in Chromium with ajv 8.20.0. Needs WebGL.

More Ajv examples

Compiling a schema with Ajv One-call validation with ajv.validate Reusing schemas with addSchema and $ref Custom formats in Ajv