1  const Ajv = require("ajv")
 2  const ajv = new Ajv({allErrors: true})
 3  
 4  const schema = {
 5    type: "object",
 6    properties: {
 7      foo: {type: "string"},
 8      bar: {type: "number", maximum: 3},
 9    },
10    required: ["foo", "bar"],
11    additionalProperties: false,
12  }
13  
14  const validate = ajv.compile(schema)
15  
16  test({foo: "abc", bar: 2})
17  test({foo: 2, bar: 4})
18  
19  function test(data) {
20    const valid = validate(data)
21    if (valid) console.log("Valid!")
22    else console.log("Invalid: " + ajv.errorsText(validate.errors))
23  }