How do I support Internet Explorer in an Angular 8 application?

Go to "tsconfig.json" and use target: "es5" instead of "target": "es2015",

target which is inside compileOnSave\compilerOptions

------Simple and Easy Way

You need to change 2 files, polyfills.ts and tsconfig.json respectively.

Just add Browser Polyfills in polyfills.ts

/***************************************************************************************************
* BROWSER POLYFILLS
*/
/** IE9, IE10 and IE11 requires all of the following polyfills. **/
import 'core-js/es6/symbol';
import 'core-js/es6/promise';
import 'core-js/es6/object';
import 'core-js/es6/function';
import 'core-js/es6/parse-int';
import 'core-js/es6/parse-float';
import 'core-js/es6/number';
import 'core-js/es6/math';
import 'core-js/es6/string';
import 'core-js/es6/date';
import 'core-js/es6/array';
import 'core-js/es6/regexp';
import 'core-js/es6/map';
import 'core-js/es6/weak-map';
import 'core-js/es6/set';

and in tsconfig.json change "target" to es5 like this

 "target": "es5", 

instead of

"target": "es2015",

According to this issue reply

You need to follow the following steps

1. Create a new tsconfig tsconfig.es5.json next to tsconfig.json with the below contents

{
 "extends": "./tsconfig.json",
 "compilerOptions": {
     "target": "es5" 
  }
}

2. In angular.json Under projects:yourAppName:architect:build:configurations, add

"es5": {
      "tsConfig": "./tsconfig.es5.json"
    }

and projects:yourAppName:architect:serve:configurations add

    "es5": {
      "browserTarget": "yourAppName:build:es5"
    }

Remember to change yourAppName in app:build:es5 to yourAppName!

full path shown below

"build": {
  "builder": "@angular-devkit/build-angular:browser",
  "options": {
      ...
  },
  "configurations": {
    "production": {
        ...
    },
    "es5": {
      "tsConfig": "./tsconfig.es5.json"
    }
  }
},
"serve": {
  "builder": "@angular-devkit/build-angular:dev-server",
  "options": {
      ...
  },
  "configurations": {
    "production": {
     ...
    },
    "es5": {
      "browserTarget": "yourAppName:build:es5"
    }
  }
},

3. Run the serve with this configuration using the below command.

ng serve --configuration es5