basant307/AI_Governance_Project

1# JavaScript ObjectSchema Package2 3by [Nicholas C. Zakas](https://humanwhocodes.com)4 5If you find this useful, please consider supporting my work with a [donation](https://humanwhocodes.com/donate).6 7## Overview8 9A JavaScript object merge/validation utility where you can define a different merge and validation strategy for each key. This is helpful when you need to validate complex data structures and then merge them in a way that is more complex than `Object.assign()`.10 11## Installation12 13You can install using either npm:14 15```16npm install @humanwhocodes/object-schema17```18 19Or Yarn:20 21```22yarn add @humanwhocodes/object-schema23```24 25## Usage26 27Use CommonJS to get access to the `ObjectSchema` constructor:28 29```js30const { ObjectSchema } = require("@humanwhocodes/object-schema");31 32const schema = new ObjectSchema({33 34    // define a definition for the "downloads" key35    downloads: {36        required: true,37        merge(value1, value2) {38            return value1 + value2;39        },40        validate(value) {41            if (typeof value !== "number") {42                throw new Error("Expected downloads to be a number.");43            }44        }45    },46 47    // define a strategy for the "versions" key48    version: {49        required: true,50        merge(value1, value2) {51            return value1.concat(value2);52        },53        validate(value) {54            if (!Array.isArray(value)) {55                throw new Error("Expected versions to be an array.");56            }57        }58    }59});60 61const record1 = {62    downloads: 25,63    versions: [64        "v1.0.0",65        "v1.1.0",66        "v1.2.0"67    ]68};69 70const record2 = {71    downloads: 125,72    versions: [73        "v2.0.0",74        "v2.1.0",75        "v3.0.0"76    ]77};78 79// make sure the records are valid80schema.validate(record1);81schema.validate(record2);82 83// merge together (schema.merge() accepts any number of objects)84const result = schema.merge(record1, record2);85 86// result looks like this:87 88const result = {89    downloads: 75,90    versions: [91        "v1.0.0",92        "v1.1.0",93        "v1.2.0",94        "v2.0.0",95        "v2.1.0",96        "v3.0.0"97    ]98};99```100 101## Tips and Tricks102 103### Named merge strategies104 105Instead of specifying a `merge()` method, you can specify one of the following strings to use a default merge strategy:106 107* `"assign"` - use `Object.assign()` to merge the two values into one object.108* `"overwrite"` - the second value always replaces the first.109* `"replace"` - the second value replaces the first if the second is not `undefined`.110 111For example:112 113```js114const schema = new ObjectSchema({115    name: {116        merge: "replace",117        validate() {}118    }119});120```121 122### Named validation strategies123 124Instead of specifying a `validate()` method, you can specify one of the following strings to use a default validation strategy:125 126* `"array"` - value must be an array.127* `"boolean"` - value must be a boolean.128* `"number"` - value must be a number.129* `"object"` - value must be an object.130* `"object?"` - value must be an object or null.131* `"string"` - value must be a string.132* `"string!"` - value must be a non-empty string.133 134For example:135 136```js137const schema = new ObjectSchema({138    name: {139        merge: "replace",140        validate: "string"141    }142});143```144 145### Subschemas146 147If you are defining a key that is, itself, an object, you can simplify the process by using a subschema. Instead of defining `merge()` and `validate()`, assign a `schema` key that contains a schema definition, like this:148 149```js150const schema = new ObjectSchema({151    name: {152        schema: {153            first: {154                merge: "replace",155                validate: "string"156            },157            last: {158                merge: "replace",159                validate: "string"160            }161        }162    }163});164 165schema.validate({166    name: {167        first: "n",168        last: "z"169    }170});171```172 173### Remove Keys During Merge174 175If the merge strategy for a key returns `undefined`, then the key will not appear in the final object. For example:176 177```js178const schema = new ObjectSchema({179    date: {180        merge() {181            return undefined;182        },183        validate(value) {184            Date.parse(value);  // throws an error when invalid185        }186    }187});188 189const object1 = { date: "5/5/2005" };190const object2 = { date: "6/6/2006" };191 192const result = schema.merge(object1, object2);193 194console.log("date" in result);  // false195```196 197### Requiring Another Key Be Present198 199If you'd like the presence of one key to require the presence of another key, you can use the `requires` property to specify an array of other properties that any key requires. For example:200 201```js202const schema = new ObjectSchema();203 204const schema = new ObjectSchema({205    date: {206        merge() {207            return undefined;208        },209        validate(value) {210            Date.parse(value);  // throws an error when invalid211        }212    },213    time: {214        requires: ["date"],215        merge(first, second) {216            return second;217        },218        validate(value) {219            // ...220        }221    }222});223 224// throws error: Key "time" requires keys "date"225schema.validate({226    time: "13:45"227});228```229 230In this example, even though `date` is an optional key, it is required to be present whenever `time` is present.231 232## License233 234BSD 3-Clause235