_saveInitialValues(initialValue) {
        // Keep the very first initial values (in the html attribute and set by the script). This is needed to check if the element is pristine.
        // Save the html attribute 'value'
        this.initialValueHtmlAttribute = AutoNumericHelper.scientificToDecimal(this.domElement.getAttribute('value'));
        if (AutoNumericHelper.isNull(this.initialValueHtmlAttribute)) {
            // Set the default empty value attribute instead of `null`, since if the initial value is null, the empty string is used
            this.initialValueHtmlAttribute = '';
        }

        // Save the 'script' value
        this.initialValue = initialValue;
        if (AutoNumericHelper.isNull(this.initialValue)) {
            // Same as above
            this.initialValue = '';
        }
    }
Save the initial element values for later use in the pristine test.
Those values are :
- the html attribute (i.e. <input value='42'>), and
- the script `value` (i.e. `let domElement.value`)

@param {null|number|string} initialValue
@private