ajv-oneOf

index.js

var AJV = require('ajv');

var schema = {
  "properties": {
    "name": { "type": "string" },
    "type": { "type": "string" },
    "constraints": {
      "properties": {
        "PRIMARY_KEY": { "type": "boolean" },
        "FOREIGN_KEY": {
          "oneOf": [
            {
              "properties": {
                "tid": { "type": "string" },
                "key": { "type": "string" }
              },
              "required": ["tid", "key"],
              "additionalProperties": false
            },
            { "type": "boolean" }
          ]
        }
      },
      "additionalProperties": false
    }
  },
  "additionalProperties": false
};

var values = [
 {
   "constraints": {
     "FOREIGN_KEY": {
       "tid": "d01",
       "key": "FD01SUMKEY"
     }
   }
 },
 {
   "constraints": {
     "FOREIGN_KEY": false
   }
 }
];

var validate = function(schema, value) { 
  console.log("in");
  try{
  	var ajv = new AJV();
  }catch(e){
    console.log(e);
  }
  var validated = ajv.validate(schema, value);
  return validated ? 'Validated successfully' : `Validation failed: ${JSON.stringify(ajv.errors)}`;
};

console.log("Validating...");
console.log(validate(schema, values[0]));
console.log(validate(schema, values[1]));

console.log("Ran successfully");

package.json

{
  "scripts": {
    "start": "node index.js"
  },
  "dependencies": {
    "ajv": "^6.2.1"
  }
}