A few lodash/fp inspired helper utility functions.

Usage no npm install needed!

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  import capeLodash from '';


cape-lodash v2.4.0

A few lodash inspired utility functions. For best results learn about _.flow() and read the Lodash FP Guide.

Install ESLint rules for lodash/fp by extending eslint with plugin:lodash-fp/recommended and including the lodash-fp plugin.


  • isFalse() - Returns true if sent a value that is exactly false.
  • isTrue() - Returns true if sent a value that is exactly true.
  • hasSize() - Opposite of isEmpty.
  • parseBoolean() - Takes a string and returns false unless word is in word list webmasterkai/affirmative
  • toBool({}) - Turn empty objects and arrays to false. Sends strings to parseBoolean. Coerce other values into a boolean.


  • changeChecker(initValue) - Returns function that accepts new val and return true if changed.
  • handleChanges(getValue, onChange) - Give it a getter and an onChange callback. It will return a function. Call returned function on every possible change and it will conditionally call onChange when it finds a change.


  • branch(bool, trueVal, falseVal) Ternary (bool ? trueVal : falseVal) in function form.
  • fpBranch(trueVal, falseVal, boolVal) Same as above with arguments order changed and curry applied.
  • condId - Each arg should be an array pair. Applied to _.cond with [ stubTrue, identity ] added as last option.
  • overBranch(boolCheck, getTrue, getFalse)


  • copy(getKey, setKey, source, target) - Value of getKey within source is added to target at setKey unless it is undefined.
  • move(getKey, setKey, object) Place value of getKey path within object to setKey path.
  • rename(renameObj, source) - renameObj = { getKey: 'setKey' }
  • renamePick(renameObj, source) - Like rename but creates a new objected limited to values of renameObj.
  • renameValues(renameObj)(strArray) - renameObj = { find: 'replace' } Similar to rename but find/replace strings in array.
  • keyWithField('id', 'value')(dataArray) - Creates a key/value index from an array of items. It's like _.keyBy but uses the field value of value property instead of the entire item.


  • merge(object, ...sources)


When you want to edit a property and return a new object instead of mutating.

  • setSimple(state, key, value) - _fp.set with normal argument order.
  • setKey(path, state, value) - set but with different arg order.
  • setKeyVal(key, value, state) - set but with different arg order.
  • setVal(value, state, key)
  • setField(path, transformer)(item) - The transformer function accepts item and should return the new value of path.
  • setFieldHas(path, transformer)(item) - Only updates if item has path. Transformer is sent entire item.
  • replaceField(path, transformer)(item) - Similar to setFieldHas. The transformer gets the value of path. Transformer must return new value that will set to path.
  • setWith(fieldId, withId, transformer) - The transformer gets the value of withId. Must return new value that will set to fieldId.


  • transformProp(transformer, path) - curried. Creates a function that returns transformation of object property at path.
  • transformPropOf(transformer, object) - curried. Same as transformProp but swap place of object/path.
  • hasMethodAt(path)(object) Returns function that evaluates if passed object has a function at path.
  • hasMethodOf(object)(path) Same as hasMethodAt with object/path flip.


Please view source for explanation and tests for usage.

  • createObj(key, value) - curried. Creates a new object with one key/val.
  • invokeArg invokes the first argument as a function.
  • invokeNthArg invokes the function at index.
  • firstValArg(0, '', 'foo') - Find the first truthy argument value.
  • getDefault('default.path', 'check.path.first') - Select two paths, send to _fp.defaultTo. Default path first.
  • oneOf([ 'array', 'of', 'options' ]) - Returns func that will return true if array contains argument.
  • divideBy divideBy(2)(4) = 2
  • isLt isLt(4)(2) = true
  • isGt isGt(2)(3) = true
  • hasOf hasOf({foo: true, bar: false})('foo') = true