canonical/node_modules/eslint-plugin-lodash/lib/rules/prefer-lodash-typecheck.js

Canonical code style linter and formatter for JavaScript, SCSS, CSS and JSON.

/**
 * @fileoverview Rule to check if there's a method in the chain start that can be in the chain
 */
'use strict';

//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------

module.exports = function (context) {
    var lodashUtil = require('../util/lodashUtil');

    var otherSides = {
        left: 'right',
        right: 'left'
    };

    function isTypeOf(node) {
        return node && node.type === 'UnaryExpression' && node.operator === 'typeof';
    }

    function isStrictComparison(node) {
        return node.operator === '===' || node.operator === '!==';
    }

    function getValueForSide(node, side) {
        var otherSide = otherSides[side];
        if (isTypeOf(node[side]) && (node[otherSide].value !== 'undefined' || node[side].argument.type !== 'Identifier')) {
            return node[otherSide].value;
        }
    }

    function getTypeofCompareType(node) {
        if (isStrictComparison(node)) {
            return getValueForSide(node, 'left') || getValueForSide(node, 'right');
        }
    }

    var REPORT_MESSAGE = 'Prefer \'_.{{method}}\' over {{actual}}.';

    return {
        BinaryExpression: function (node) {
            var typeofCompareType = getTypeofCompareType(node);
            if (typeofCompareType) {
                context.report(node, REPORT_MESSAGE, {
                    method: lodashUtil.getIsTypeMethod(typeofCompareType),
                    actual: '\'typeof\' comparison'
                });
            } else if (node.operator === 'instanceof') {
                var lodashEquivalent = lodashUtil.getIsTypeMethod(node.right.name);
                if (node.right.type === 'Identifier' && lodashEquivalent) {
                    context.report(node, REPORT_MESSAGE, {method: lodashEquivalent, actual: '\'instanceof ' + node.right.name + '\''});
                }
            }
        }
    };
};