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How to use the isFunction function from lodash

Find comprehensive JavaScript lodash.isFunction code examples handpicked from public code repositorys.

In JavaScript, _.isFunction is a function in the Lodash library that checks whether a value is a function or not.

astrobench.js

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 * @category Objects
 * @param {*} value The value to check.
 * @returns {boolean} Returns `true` if the `value` is a function, else `false`.
 * @example
 *
 * _.isFunction(_);
 * // => true
 */
function isFunction(value) {
  return typeof value == 'function';

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utils.js

GitHub: compdemocracy/polis

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}


function mapObj(o, f) {
  var out = {};


  var ff = _.isFunction(f) ? function(val, key) {
    out[key] = f(val, key);
  } : function(val, key) {
    out[key] = o[key];
  };

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+ 4 other calls in file

How does lodash.isFunction work?

_.isFunction is a function in the Lodash library for JavaScript that checks whether a value is a function or not.

When _.isFunction is called with a value as input, it performs the following operations:

It returns true if the value is a function, false otherwise.
To check if the value is a function, it checks whether the typeof the value is "function".
If the typeof check returns true, _.isFunction also checks whether the value is a constructor function or a non-native function created by the Function constructor.

By using _.isFunction, developers can easily determine whether a value is a function or not, which can be useful for conditionally executing code or passing functions as arguments to other functions. Note that _.isFunction does not perform any type coercion or type checking beyond checking the typeof the value, so it may return unexpected results if used improperly.

request-helpers-presend.js

GitHub: postmanlabs/postman-runtime

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    function (config, cb) {
        if (config) {
            return cb(null, config);
        }

        return _.isFunction(run.options.systemProxy) ? run.options.systemProxy(url, cb) : cb(null, undefined);
    }
], function (err, config) {
    if (err) {
        run.triggers.console(context.coords, 'warn', 'proxy lookup error: ' + (err.message || err));

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lodash-contrib.commonjs.js

GitHub: node4good/lodash-contrib

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module.exports.isEqualWith         = _.isEqualWith;
module.exports.isError             = _.isError;
module.exports.isEven              = _.isEven;
module.exports.isFinite            = _.isFinite;
module.exports.isFloat             = _.isFloat;
module.exports.isFunction          = _.isFunction;
module.exports.isIncreasing        = _.isIncreasing;
module.exports.isIndexed           = _.isIndexed;
module.exports.isInstanceOf        = _.isInstanceOf;
module.exports.isInteger           = _.isInteger;

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+ 92 other calls in file

Ai Example

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const _ = require("lodash");

function multiply(a, b) {
  return a * b;
}

const num = 5;
const isFunc = _.isFunction(multiply);

console.log(isFunc); // Outputs: true
console.log(_.isFunction(num)); // Outputs: false

In this example, we're using _.isFunction to check whether the multiply function is actually a function or not. We provide multiply as input to _.isFunction, which returns true since multiply is indeed a function. We also check whether the num variable is a function or not, which returns false since num is a number, not a function.

contentful.js

GitHub: nsbarsukov/ml-bug-detector

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    // with `object` as context and arguments; otherwise, return undefined.
    attempt: function(object, method) {
      if (object == null) return void 0;
      var func = object[method];
      var args = slice.call(arguments, 2);
      return _.isFunction(func) ? func.apply(object, args) : void 0;
    }
  });


})(this);

+ 117 other calls in file

model.js

GitHub: maxprogram/grand-central-records

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    }
    return false;
}

// Check value type
if (_.isArray(type) && _.isFunction(type[0])) {
    if (!_.isArray(value)) return msg('wrongType','array');
    type = type[0];
    value = value[0];
}

+ 15 other calls in file

utils.ts

GitHub: JamilOmar/lsc

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assert.ok(
  _.isString(packagePath),
  'applyToNodeModulesSync: `packagePath` must be a non-empty string',
);
assert.ok(
  _.isFunction(func),
  'applyToNodeModulesSync: `func` must be a function',
);

if (!isPackageSync(packagePath)) {

db.js

GitHub: sdaigle2/Abacus-mvp

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 */
// _.forEach(EXPORTED_DBS, db => {
//   db.deleteDoc = function (docID, docRev, cb) {
//     var givenDocID = _.isString(docID) || _.isNumber(docID);
//     var givenDocRev = _.isString(docRev);
//     var givenCallback = _.isFunction(cb);


//     if (givenDocID && givenDocRev && givenCallback) {
//       db.destroy(docID, docRev, cb);
//     } else if (givenCallback) {

+ 12 other calls in file

index.js

GitHub: bitfinexcom/grenache-nodejs-link

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const req = {
  rid: rid,
  type: type,
  payload: payload,
  opts: opts,
  cb: _.isFunction(cb) ? cb : () => {},
  _ts: Date.now()
}

req.qhash = this.getRequestHash(type, payload)

cli-yo.js

GitHub: TryGhost/slimer

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        debug('init with', obj);


        generator.run(() => {
            debug('return with', generator.props);
            return _.isFunction(cb) ? cb(generator.props) : generator.props;
        });
    }
}

lodash.js

GitHub: mdmarufsarker/lodash

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console.log(isError); // => true


const isFinite = _.isFinite(1);
console.log(isFinite); // => true


const isFunction = _.isFunction(() => {});
console.log(isFunction); // => true


const isInteger = _.isInteger(1);
console.log(isInteger); // => true

+ 15 other calls in file

index.js

GitHub: Arxivar/PluginGenerator

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  }
  Object.keys(this.options.arxivarPluginSettings).forEach(key => {
    const prompt = _.isNil(prompts) ? undefined : prompts.find(p => p.name === key);
    const value = this.options.arxivarPluginSettings[key]
    if (!_.isNil(prompt) && !_.isNil(prompt.default) && _.isNil(value)) {
      this.options.arxivarPluginSettings[key] = _.isFunction(prompt.default) ? prompt.default(this.options.arxivarPluginSettings) : prompt.default
    }
  });
  return Promise.resolve(this.options.arxivarPluginSettings)
}

router.js

GitHub: enyosolutions-team/axel-core

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if (axel.config.policies['*']) {
  if (Array.isArray(axel.config.policies['*'])) {
    policies = policies.concat(axel.config.policies['*']);
  } else if (
    _.isString(axel.config.policies['*'])
    || _.isFunction(axel.config.policies['*'])
  ) {
    policies.push(axel.config.policies['*']);
  }
}

index.js

GitHub: Eveble/eveble

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        this.ejson.addType(typeName, factory);
    }
}
createFactory(type) {
    const construct = function (serializer, TypeCtor, json) {
        const propTypes = lodash.isFunction(TypeCtor.getPropTypes)
            ? TypeCtor.getPropTypes()
            : {};
        for (const key of Object.keys(propTypes)) {
            if (json[key]) {

+ 9 other calls in file

validate.js

GitHub: th3rdwave/serverless-rspack

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  return BbPromise.resolve();
};

// Rspack config can be a Promise, If it's a Promise wait for resolved config object.
if (this.rspackConfig && _.isFunction(this.rspackConfig.then)) {
  return BbPromise.resolve(
    this.rspackConfig.then((config) => processConfig(config)),
  );
}

index.js

GitHub: nodejs-tutorials/hello-ghost

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if (!_.isNull(appPermissions)) {
    hasAppPermission = _.any(appPermissions, checkPermission);
}

// Offer a chance for the TargetModel to override the results
if (TargetModel && _.isFunction(TargetModel.permissible)) {
    return TargetModel.permissible(
        modelId, actType, context, loadedPermissions, hasUserPermission, hasAppPermission
    );
}

util.js

GitHub: apHarmony/jsharmony-db

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exports.escapeRegEx = function (q) {
  return q.replace(/[-[\]{}()*+?.,\\/^$|#\s]/g, '\\$&');
};
exports.flattenDBTasks = function(dbtasks, accumulator){
  if(!accumulator){
    if(_.isArray(dbtasks) && dbtasks.length && _.isFunction(dbtasks[0])) accumulator = [];
    else accumulator = {};
  }
  _.each(dbtasks, function(val, key){
    if(_.isFunction(val)){

+ 6 other calls in file

index.js

GitHub: MomsFriendlyDevCo/generic-cache

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*/
cache.can = func => {
	switch (func) {
		case 'clear':
		case 'clean':
			return _.isFunction(cache.activeModule[func])
			|| (_.isFunction(cache.activeModule.list) && _.isFunction(cache.activeModule.unset))
		default: // Also includes 'list'
			return !! _.isFunction(cache.activeModule[func]);
	}

+ 11 other calls in file

index.cjs

GitHub: vzakharov/vovas-utils-ts

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function _log(options, ...args) {
  const { color, serializeAs } = _.defaults(options, defaultOptions);
  if (loggerInfo.logAll || index === "always" || index === loggerInfo.lastLogIndex) {
    console.log(...args.map(
      (arg) => String(
        isPrimitive(arg) ? arg : _.isFunction(arg) ? arg.toString() : $try(() => serializer[serializeAs](arg), arg)
      ).split("\n").map(paint[color]).join("\n")
    ));
  }
}

+ 14 other calls in file

serializer.js

GitHub: krieit/Node-vogels

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    return internals.createSet(vals, 'B');
  }
};


internals.deserializeAttribute = function (value) {
  if(_.isObject(value) && _.isFunction(value.detectType) && _.isArray(value.values)) {
    // value is a Set object from document client 
    return value.values;
  } else {
    return value;

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