operator_exponent: this.exponent,

exponent (args) {
  return Cast.toNumber(args.NUM1) ** Cast.toNumber(args.NUM2);
}

'<block type="operator_exponent" id="operator_exponent">' +
 '<value name="NUM1">' +
    '<shadow type="math_number">' +
  '<field name="NUM"></field>' +
  '</shadow>' +
'</value>' +

Blockly.Blocks['operator_exponent'] = {
  /**
   * Block for raising one number to the power of another. 
  * @this Blockly.Block
  */
  init: function() {
    this.jsonInit({
      "message0": Blockly.Msg.OPERATORS_EXPONENT,
      "args0": [
        {
         "type": "input_value",
          "name": "NUM1"
        },
        {
          "type": "input_value",
          "name": "NUM2"
        }
      ],
     "category": Blockly.Categories.operators,
     "extensions": ["colours_operators", "output_number"]
    });
  }
};

Blockly.Msg.OPERATORS_EXPONENT = '%1 ^ %2';

<block type="operator_exponent">
   <value name="NUM1">
   <shadow type="math_number">
      <field name="NUM"/>
    </shadow>
   </value>
   <value name="NUM2">
   <shadow type="math_number">
     <field name="NUM"/>
    </shadow>
  </value>
</block>

test('exponent', t => {
  t.strictEqual(blocks.exponent({NUM1: '2', NUM2: '3'}), 8);
  t.strictEqual(blocks.exponent({NUM1: 'foo', NUM2: 'bar'}), 1);
  t.end();
});

test('exponent: exponentiation with Infinity', t => {
  t.strictEqual(
    blocks.exponent({NUM1: 'Infinity', NUM2: 111}), Infinity, '"Infinity" ^ 111 = Infinity'
  );
  t.strictEqual(
    blocks.exponent({NUM1: 'INFINITY', NUM2: 222}), 0, '"INFINITY" ^ 222 = 0'
  );
  t.strictEqual(
   blocks.exponent({NUM1: Infinity, NUM2: 333}), Infinity, 'Infinity ^ 333 = Infinity'
   );
  t.strictEqual(
    blocks.exponent({NUM1: 111, NUM2: 'Infinity'}), Infinity, '111 ^ "Infinity" = Infinity'
  );
  t.strictEqual(
    blocks.exponent({NUM1: 222, NUM2: 'INFINITY'}), 1, '222 ^ "INFINITY" = 1'
  );
  t.strictEqual(
    blocks.exponent({NUM1: 333, NUM2: Infinity}), Infinity, '333 ^ Infinity = Infinity'
  );
  t.strictEqual(
    blocks.exponent({NUM1: '-Infinity', NUM2: 111}), -Infinity, '"-Infinity" ^ 111 = -Infinity'
  );
  t.strictEqual(
    blocks.exponent({NUM1: '-INFINITY', NUM2: 222}), 0, '"-INFINITY" ^ 222 = 0'
  );
  t.strictEqual(
    blocks.exponent({NUM1: -Infinity, NUM2: 333}), -Infinity, '-Infinity ^ 333 = -Infinity'
  );
  t.strictEqual(
    blocks.exponent({NUM1: 111, NUM2: '-Infinity'}), 0, '111 ^ "-Infinity" = 0'
  );
  t.strictEqual(
    blocks.exponent({NUM1: 222, NUM2: '-INFINITY'}), 1, '222 ^ "-INFINITY" = 1'
  );
  t.strictEqual(
    blocks.exponent({NUM1: 333, NUM2: -Infinity}), 0, '333 ^ -Infinity = 0'
  );
  t.end();
});

<block type="operator_exponent">
  <value name="NUM1">
  <shadow type="math_number">
    <field name="NUM"></field>
  </shadow>
  </value>
  <value name="NUM2">
          <shadow type="math_number">
           <field name="NUM"></field>
          </shadow>
        </value>
      </block>