feat: support toBigInt method

bignumber.d.ts

@@ -1423,6 +1423,19 @@ export declare class BigNumber implements BigNumber.Instance {
    */
   toNumber(): number;
 
+  /**
+   * Returns the value of this BigNumber as a JavaScript primitive BigInt.
+   *
+   * ```ts
+   * x = new BigNumber(456)
+   * x.toBigInt()                    // 456n
+   *
+   * y = new BigNumber('45987349857634085409857349856430985')
+   * y.toBigInt()                    // 45987349857634085409857349856430985n
+   * ```
+   */
+  toBigInt(): BigInt;
+
   /**
    * Returns a string representing the value of this BigNumber rounded to `significantDigits`
    * significant digits using rounding mode `roundingMode`.

bignumber.js

@@ -42,6 +42,7 @@
  *      toFraction                      |
  *      toJSON                          |
  *      toNumber                        |
+ *      toBigInt                        |
  *      toPrecision                     |
  *      toString                        |
  *      valueOf                         |
@@ -2694,6 +2695,15 @@
       return +valueOf(this);
     };
 
+    /*
+     * Return the value of this BigNumber converted to a BigInt primitive.
+     */
+    P.toBigInt = function () {
+      if (!this.isInteger()) throw Error(bignumberError + 'Not an integer: ' + valueOf(this));
+      var str = coeffToString(this.c);
+      for (var i = this.e + 1 - str.length; i > 0; i--) str += '0';
+      return BigInt(this.s < 0 ? '-' + str : str);
+    };
 
     /*
      * Return a string representing the value of this BigNumber rounded to sd significant digits

bignumber.mjs

@@ -39,6 +39,7 @@
  *      toFraction                      |
  *      toJSON                          |
  *      toNumber                        |
+ *      toBigInt                        |
  *      toPrecision                     |
  *      toString                        |
  *      valueOf                         |
@@ -2669,6 +2670,16 @@ function clone(configObject) {
     return +valueOf(this);
   };
 
+  /*
+   * Return the value of this BigNumber converted to a BigInt primitive.
+   */
+  P.toBigInt = function () {
+    if (!this.isInteger()) throw Error(bignumberError + 'Not an integer: ' + valueOf(this));
+    var str = coeffToString(this.c);
+    for (var i = this.e + 1 - str.length; i > 0; i--) str += '0';
+    return BigInt(this.s < 0 ? '-' + str : str);
+  };
+
 
   /*
    * Return a string representing the value of this BigNumber rounded to sd significant digits

doc/API.html

@@ -141,6 +141,7 @@
       <li><a href="#toFr"   >toFraction            </a>                  </li>
       <li><a href="#toJSON" >toJSON                </a>                  </li>
       <li><a href="#toN"    >toNumber              </a>                  </li>
+      <li><a href="#toB"    >toBigInt              </a>                  </li>
       <li><a href="#toP"    >toPrecision           </a>                  </li>
       <li><a href="#toS"    >toString              </a>                  </li>
       <li><a href="#valueOf">valueOf               </a>                  </li>
@@ -1761,6 +1762,16 @@ <h5 id="toN">toNumber<code class='inset'>.toNumber() <i>&rArr; number</i></code>
 1 / z.toNumber()                // -Infinity
 1 / +z                          // -Infinity</pre>
 
+    <h5 id="toB">toBigInt<code class='inset'>.toBigInt() <i>&rArr; BigInt</i></code></h5>
+    <p>Returns the value of this BigNumber as a JavaScript BigInt primitive.</p>
+    <pre>
+x = new BigNumber(456)
+x.toBigInt()                    // 456n
+
+y = new BigNumber('45987349857634085409857349856430985')
+y.toBigInt()                    // 45987349857634085409857349856430985n
+</pre>
+
 
 
     <h5 id="toP">

test/methods/toBigInt.js

@@ -0,0 +1,46 @@
+if (typeof Test === 'undefined') require('../tester');
+
+Test('toBigInt', function () {
+
+    function t(value, n) {
+        Test.areEqual(n, new BigNumber(value).toBigInt());
+    }
+
+    function tx(fn, msg){
+        Test.isException(fn, msg);
+    }
+
+    t(0, 0n);
+    t(-0, 0n);
+    t(1, 1n);
+    t(1, 1n);
+    t(-1, -1n);
+    t('-1', -1n);
+    t('1.0', 1n);
+    t('-1.0', -1n);
+    t('11111.0000', 11111n);
+    t('-11111.0000', -11111n);
+
+    t('1234567890000000', 1234567890000000n);
+    t('1234567890000000', 1234567890000000n);
+    t('-1234567890000000', -1234567890000000n);
+    t('1e18', BigInt(1e18));
+    t('-1e18', BigInt(-1e18));
+
+    // large integers
+    t('1e50', BigInt(`1${'0'.repeat(50)}`));
+    t('-1e50', BigInt(`-1${'0'.repeat(50)}`));
+    t('1e100', BigInt(`1${'0'.repeat(100)}`));
+
+    // non-integers
+    tx(() => new BigNumber(null).toBigInt(), '(null)');
+    tx(() => new BigNumber(NaN).toBigInt(), '(NaN)');
+    tx(() => new BigNumber(Infinity).toBigInt(), '(Infinity)');
+    tx(() => new BigNumber(-Infinity).toBigInt(), '(-Infinity)');
+    tx(() => new BigNumber('123abcdefg').toBigInt(), '(123abcdefg)');
+    tx(() => new BigNumber('abcdefg').toBigInt(), '(abcdefg)');
+    tx(() => new BigNumber(1.1).toBigInt(), '(1.1)');
+    tx(() => new BigNumber(-1.1).toBigInt(), '(-1.1)');
+    tx(() => new BigNumber(123123123.123).toBigInt(), '(123123123.123)');
+    tx(() => new BigNumber(321.123).toBigInt(), '(321.123)');
+});

test/test.html

@@ -43,6 +43,7 @@
     'toFormat',
     'toFraction',
     'toNumber',
+    'toBigInt',
     'toPrecision',
     'toString'
   ];

test/test.js

@@ -33,6 +33,7 @@ console.log('\n Testing bignumber.js\n');
   'toFormat',
   'toFraction',
   'toNumber',
+  'toBigInt',
   'toPrecision',
   'toString'
 ]