repr()

This module is intended to make short, limited string representations of complex object.

For a more detailed inspection tool, try @whi/json which has a json.debug() method for deep representational inspection.

Overview

The main use-case for this library is expected to be for logging.

Features

• Distinguish primitive types from their similar object version
• Truncate large list types
• Support for
  • Map types:
    • Boolean, Number, String, Date, RegExp, Function, Object
  • List types:
    • Array, Int8Array, Uint8Array, Uint8ClampedArray, Int16Array, Uint16Array, Int32Array, Uint32Array, Float32Array, Float64Array, BigInt64Array, BigUint64Array
  • Primitive types:
    • string, number, bigint, boolean, null, undefined, symbol
• Custom object formatting by implementing a toRepr() method.

Install

npm i @whi/repr

Usage

The default import is a single function.

const repr = require('@whi/repr');

Pass any value to repr to get the representational value.

const value = [0,1,2,3,4,5,6,7,8,9];

repr( input )
// Array (10) [ 0, 1, 2, 3 … 6, 7, 8, 9 ]

repr( input, true );
// Array(10)

const value = {a:0,b:0,c:0,d:0,e:0,f:0,g:0,h:0,i:0,j:0};

repr( input )
// Object { a: 0, b: 0, c: 0, d: 0 … 6 more properties }

repr( input, true );
// Object(10)

Second-level values are automatically displayed using the minimal format.

const value = [ [], {}, new Boolean(1), new Number(1), new String("hi"), new Date(1646429736851), RegExp(/.*/gi), () => {} ];

repr( input )
// Array (8) [ Array(0), Object(0), Bool(1), Number(1), String("hi"), 2022-03-04T21:35:36.851Z, RegExp(/.*/gi), function(0 args) ]

repr( input, true );
// Array(8)

Custom formatting

class Rectangle {
    constructor ( x, y ) {
        this.x = x;
        this.y = y;
    }

    toRepr ( minimal ) {
        return minimal
            ? `${this.constructor.name}(${this.x},${this.y})`
            : `${this.constructor.name} { x: ${this.x}, y: ${this.y} }`;
    }
}

const value = new Rectangle( 3, 4 );

repr( value )
// Rectangle { x: 3, y: 4 }

repr( value, true )
// Rectangle(3,4)

Contributing

See CONTRIBUTING.md