lib/util.js
function isInstalled(dep) {
    if (_.has(exceptions, dep)) return exceptions[dep];
    return installedDeps.has(dep);
}
function isInstalled(dep) {
    if (_.has(exceptions, dep)) return exceptions[dep];
    return installedDeps.has(dep);
}
function isInstalled ( dep ) { if ( _ . has ( exceptions , dep ) ) return exceptions [ dep ] ; return installedDeps . has ( dep ) ; }
Check if the given dependency is installed.
Checks against `dependencies`, `devDependencies` in project `package.json`.

@param {string} dep Name of the dependency
@returns {boolean} `true` if installed, `false` if not
Check if the given dependency is installed . Checks against dependencies devDependencies in project package . json .