const regex = /<span\b[^>]*+>(?# Открывающий span с любыми атребутами
)\s*+(?# Пробелы
)(?<number>\-?+\d++(?:[\.\,]\d++)?+)(?# Число
)\s*+(?# Пробелы
)<\/span>(?# Закрывающий span)/gus;
// Alternative syntax using RegExp constructor
// const regex = new RegExp('<span\\b[^>]*+>(?# Открывающий span с любыми атребутами
)\\s*+(?# Пробелы
)(?<number>\\-?+\\d++(?:[\\.\\,]\\d++)?+)(?# Число
)\\s*+(?# Пробелы
)<\\\/span>(?# Закрывающий span)', 'gus')
const str = `<span class="company__segment__inner">0</span>
<span class="company__segment__inner">1</span>
<span class="company__segment__inner">1.</span>
<span class="company__segment__inner">1.0</span>
<span class="company__segment__inner">-1</span>
<span class="company__segment__inner">12121.12212</span>
<span class="company__segment__inner">192.168.0.1</span>
<span class="company__segment__inner">Только числа</span>
<span>1</span>
<spank>1</spank>
<span>-0,123</span>
<span>
-0,123
</span>`;
const subst = `${number}`;
// The substituted value will be contained in the result variable
const result = str.replace(regex, subst);
console.log('Substitution result: ', result);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for JavaScript, please visit: https://developer.mozilla.org/en/docs/Web/JavaScript/Guide/Regular_Expressions