budget-calculator-5.js

// Polymer template code
<p>Your closest income band is {{results.income}}. Figures for a {{sheetLabel}}.</p>

<div class="row">
  <div class="col">
    <div class="label">Income change next year (2018/19)</div>
    <div class="big income">{{results.change_2018}}</div>
  </div>
</div>

<div class="row borderTop">
  <div class="col">
    <div class="label">Current net income (2017/18)</div>
    <div class="big mid">{{results.total_income_2017}}</div>
    <div class="label gill">after a {{results.tax_nic_bill_2017}} tax deduction</div>
  </div>
  <div class="col">
    <div class="label">Net year's net income (2018/19)</div>
    <div class="big mid">{{results.total_income_2018}}</div>
    <div class="label gill">after a {{results.tax_nic_bill_2018}} tax deduction</div>
  </div>
</div>

<div class="row borderBottom">
  <div class="col">
    <div class="label">Current child benefit (2017/18)</div>
    <div class="big mid">{{results.child_benefit_2017}}</div>
  </div>
  <div class="col">
    <div class="label">Next year's child benefit (2018/19)</div>
    <div class="big mid">{{results.child_benefit_2018}}</div>
  </div>
</div>


// Polymer JavaScript code
const rawIncomeBracketData = {
  change_2018: 283,
  change_2019: 0,
  child_benefit_2017: 0,
  child_benefit_2018: 0,
  child_benefit_2019: 0,
  income: 120000,
  student_loan_repayment_2017: 9200,
  student_loan_repayment_2018: 9150,
  student_loan_repayment_2019: 9150,
  tax_nic_bill_2017: 46620,
  tax_nic_bill_2018: 46387,
  tax_nic_bill_2019: 46387,
  total_income_2017: 64180,
  total_income_2018: 64463,
  total_income_2019: 64463,
  universal_credit_2017: 0,
  universal_credit_2018: 0,
  universal_credit_2019: 0
};

this.results = Object.keys(rawIncomeBracketData)
  .reduce((acc, key) => {
    const value = rawIncomeBracketData[key];

    let prefix = '';
    switch(key) {
      case 'change_2018':
        prefix = value < 0 ? '-' : '+';
        break;
    }

    return Object.assign(acc, {
      [key]: `${prefix}£${Math.abs(value).toLocaleString()}`
    });
  }, {});