add after ary assign assignIn assignInWith assignWith at before bind bindAll bindKey camelCase capitalize castArray ceil chain chunk clamp clone cloneDeep cloneDeepWith cloneWith compact concat conformsTo countBy create curry curryRight debounce deburr defaults defaultsDeep defer delay difference divide drop dropRight each eachRight endsWith entries entriesIn eq escape every extend extendWith fill filter find findIndex findKey findLast findLastIndex findLastKey first flatMap flatMapDeep flatMapDepth flatten flattenDeep flattenDepth flip floor forEach forEachRight forIn forInRight forOwn forOwnRight fromPairs functions functionsIn get groupBy gt gte has hasIn head inRange includes indexOf initial intersection invert invertBy invoke invokeMap isArguments isArray isArrayBuffer isArrayLike isArrayLikeObject isBoolean isBuffer isDate isElement isEmpty isEqual isEqualWith isError isFinite isFunction isInteger isLength isMap isMatch isMatchWith isNaN isNative isNil isNull isNumber isObject isObjectLike isPlainObject isRegExp isSafeInteger isSet isString isSymbol isTypedArray isUndefined isWeakMap isWeakSet join kebabCase keyBy keys keysIn last lastIndexOf lowerCase lowerFirst lt lte map mapKeys mapValues max maxBy mean meanBy memoize merge mergeWith min minBy multiply negate nth omit omitBy once orderBy overArgs pad padEnd padStart parseInt partial partialRight partition pick pickBy pull pullAll pullAllBy pullAllWith pullAt random rearg reduce reduceRight reject remove repeat replace rest result reverse round sample sampleSize set setWith shuffle size slice snakeCase some sortBy sortedIndex sortedIndexOf sortedLastIndex sortedLastIndexOf sortedUniq split spread startCase startsWith subtract sum sumBy tail take takeRight tap template throttle thru toArray toFinite toInteger toLength toLower toNumber toPairs toPairsIn toPlainObject toSafeInteger toString toUpper transform trim trimEnd trimStart truncate unary unescape union uniq uniqBy uniqWith unset unzip unzipWith update updateWith upperCase upperFirst values valuesIn without words wrap wrapperAt wrapperChain wrapperCommit wrapperFlatMap wrapperLodash wrapperNext wrapperPlant wrapperReverse wrapperToIterator wrapperValue xor zip zipObject zipObjectDeep zipWith

Lodash _.assignIn

Overview

The lodash _.assignIn method is a utility function in the lodash library that allows you to merge two or more objects together into a single object. This function acts as a wrapper around the native Javascript Object.assign method, but with added functionality and handling some edge cases.

With _.assignIn, you can copy own and inherited properties from the source objects to a target object. This means that any properties that exist in the source objects will be copied to the target object, overwriting any properties with the same name that already exist in the target object. Additionally, if there are properties that exist in an object's prototype chain, those properties will also be copied to the target object.

Here's an example of how to use _.assignIn:

const _ = require('lodash');

const target = {
   name: 'George',
   age: 30,
};

const source = {
   age: 50,
   occupation: 'Developer',
};

const result = _.assignIn(target, source);
console.log(result);

/* Output:
   {
      name: 'George',
      age: 50,
      occupation: 'Developer',
   }
*/

In this example, we have a target object with two properties (name and age). We also have a source object with two properties (age and occupation). When we use _.assignIn to merge these two objects, the resulting object contains all four properties, with the age property being overwritten by the source object's age value.

There are a few things to keep in mind when using _.assignIn:

  • The first argument passed to the function is treated as the target object, and will be modified in place. If you need to preserve the original target object, you should create a copy of it before using _.assignIn.
  • If you pass in more than two objects to _.assignIn, they will be merged in order, with later objects overwriting properties from earlier objects.
  • If any of the source objects have circular references (where an object refers to itself, either directly or indirectly), _.assignIn may go into an infinite loop and cause the program to crash. Overall, _.assignIn is a useful tool for merging objects in Javascript, and can help simplify code and reduce duplication.