TypeScript import helpers (import-helpers)

typescript-config/import-helpers checks if the property importHelpers is enabled in your TypeScript configuration file (i.e. tsconfig.json) and that the tslib package is installed.

Why is this important?

By enabling the importHelpers compiler option of TypeScript, the compiler will use the tslib package and reduce the size of the output. E.g.:

var __assign = (this && this.__assign) || Object.assign || function(t) {
    for (var s, i = 1, n = arguments.length; i < n; i++) {
        s = arguments[i];
        for (var p in s) if (Object.prototype.hasOwnProperty.call(s, p))
            t[p] = s[p];
    }
    return t;
};
exports.x = {};
exports.y = __assign({}, exports.x);

var tslib_1 = require("tslib");
exports.x = {};
exports.y = tslib_1.__assign({}, exports.x);

What does the hint check?

This hint checks if the compilerOptions property importHelpers is enabled.

Examples that trigger the hint

By default, TypeScript doesn’t enable importHelpers:

{
    ...
    "compilerOptions": {
        "target": "es5",
        ...
    },
    ...
}

Also setting the value to false will fail:

{
    ...
    "compilerOptions": {
        "importHelpers": false,
        ...
    },
    ...
}

Examples that pass the hint

importHelpers value is true:

{
    "compilerOptions": {
        "importHelpers": true,
        ...
    },
    ...
}

Further Reading

• TypeScript Documentation
• tslib Documentation