Boolean

If true, specifies that the property uniquely identifies instances of the type. identity configures the result of getIdentity.

The following specifies that the id property values uniquely identifies Todo instances:

import {DefineMap, Reflect as canReflect} from "can";

const Todo = DefineMap.extend("Todo",{
    id: {type: "number", identity: true},
    name: "string",
    complete: "boolean"
});

const todo = new Todo({id: 6, name: "mow lawn"});

console.log( canReflect.getIdentity(todo) ); //-> 6

identity can be true for multiple properties. If multiple identity properties are specified, a sorted JSON string is returned:

import {DefineMap, Reflect as canReflect} from "can";

const Grade = DefineMap.extend("Grade",{
    classId: {type: "number", identity: true},
    studentId: {type: "number", identity: true},
    grade: "string"
});

const grade = new Grade({classId: 5, studentId: 7, grade: "A+"});

console.log( canReflect.getIdentity(grade) ); //-> "{'classId':5,'studentId':7}"