Qfyilyi

Try the following steps,

Step 1:

npm update -g @angular/cli

Step 2:

Edit your package.json changing the line

"@angular/cli": "1.6.0",

to

"@angular/cli": "^1.6.0",

STEP 3:

npm update

Refer the steps

Step1: Edit your package.json changing the line

@angular/cli": "1.6.4"

to

@angular/cli": "^1.6.4"

Step2:

npm update -g @angular/cli 

Step3:

npm install --save-dev @angular/cli@latest

I was facing the exact same problem. These three did the tasks for me. You may like to see https://github.com/angular/angular-cli/issues/9307

try this out

npm install @angular-devkit/core --save-dev

https://github.com/angular/devkit/issues/256

try to update your angular cli

https://github.com/angular/angular-cli/issues/9307

This can happen on different versions on angular-cli.
You can install it manually with

 npm i -D @angular-devkit/core 

-D is shortcut to --save-dev

Or try the latest version of angular cli

npm install --save-dev @angular/cli@latest

package.json, change to "@angular/cli": "^1.6.5",

 "devDependencies": {

"@angular/cli": "^1.6.5",

"@angular/compiler-cli": "^5.0.0",

Important, the version could be vary depends on what time.

You really should run

 npm update -g @angular/cli 

first, to get version, my is 1.6.5

What does the "^" do?

 ~1.0.2 means to install version 1.0.2 or the latest patch version such as 1.0.4. 



  ^1.0.2 means to install version 1.0.2 or the latest minor or patch version such as 1.1.0.

last, run this

   npm update

Just run:

npm install --save-dev @angular/cli@latest

In the project folder, to fix it.

You can do

First,

Delete the node_modules folder

Run npm install

And add devkit to your dev dependancies with npm i -D @angular-devkit/core

Step 1: delete package-lock.json
Step 2: npm update -g @angular/cli
Step 3: update @angular/cli new version in package.json
Step 4: npm install

It worked for me.

I only installed my angular/cli using:
npm install -g @angular/cli@1.5.2

And I started getting this error.

Solution:

If your version is global and

If you don't mind the version of your angular/cli then type:
npm update -g @angular/cli

This is what worked for me,

Go to the folder where you have the project from command line.
run the command:
npm install @angular-devkit/core

If you see the above image, I found some vulnerabilities which needed to fixed.

run the following commands in sequence:
Step 1: npm audit fix
Step 2: npm install