The same issue:
ERROR in node_modules/exceljs/index.d.ts(1661,34): error TS2503: Cannot find namespace 'NodeJS'.
"@angular/cli": "~7.0.4",
"@types/node": "~8.9.4",
"exceljs": "^3.3.0",

Failed to compile.

node_modules/exceljs/index.d.ts(1661,34): error TS2503: Cannot find namespace 'NodeJS'.
Tried with npm install after the installing specific package installation but still facing the same issue.

Same error for me

"@angular/animations": "~7.2.0",
"@angular/common": "~7.2.0",
"@angular/compiler": "~7.2.0",
"@angular/core": "~7.2.0",
"@angular/forms": "~7.2.0",
"@angular/platform-browser": "~7.2.0",
"@angular/platform-browser-dynamic": "~7.2.0",
"@angular/router": "~7.2.0",
"core-js": "^2.5.4",
"exceljs": "^3.3.0",
"file-saver": "^2.0.2",

I am getting the same error: ERROR in node_modules/exceljs/index.d.ts(1661,34): error TS2503: Cannot find namespace 'NodeJS'. I tried the suggestions in #971, but none of those worked for me. Anyone find a fix yet?
"exceljs": "^3.3.1"
"core-js": "^2.6.10"
"@angular-devkit/build-angular": "^0.13.9",
"@angular/animations": "^7.2.15",
"@angular/cli": "^7.3.9",
"@angular/common": "^7.2.15",
@angular/compiler": "^7.2.15",
"@angular/compiler-cli": "^7.2.15",
"@angular/core": "^7.2.15",
"@angular/forms": "^7.2.15",
"@angular/http": "^7.2.15",
"@angular/language-service": "^7.2.15",
"@angular/platform-browser": "^7.2.15",
"@angular/platform-browser-dynamic": "^7.2.15",
"@angular/router": "^7.2.15",
"typescript": "^3.2.4"
"webpack": "^4.41.2"

same thing goes for me

I tried to add "node" in tsconfig.json、tsconfig.app.json .

Then got the error:

ERROR in node_modules/exceljs/index.d.ts(1661,41): error TS2694: Namespace 'NodeJS' has no exported member 'TypedArray'

-> update @types/node

And referenced this #971 (comment), edited my code like below:

const Excel = require('exceljs');
const workbook = new Excel.Workbook();

It works for me !

@jeanfliu Yes, it worked for me also but the drawback is you do not have type suggestions in editor

I erase the NodeJS.TypedArray from "index.d.ts" in de "node_modules/exceljs"

that works for me :)

not the best form to fix it but works

Thanks for opening this request.
Please re-open if you still have issues.
Best of luck.