Scalar styling§

Scalar styling controls how strings are written without changing their values: plain, quoted, literal (|), or folded (>).

The presenter provides default rules that choose string styles based on their content. If those defaults do not suit your needs, customize them with the scalarStyleRules option.

Example: allow tabs in block scalars§

By default, dump() writes strings containing tabs with double quotes so the tabs are visible:

text: "first line\n\tindented line\n"
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Tabs are also valid inside block scalars. If you prefer to allow tabs in block scalars:

import { DEFAULT_SCALAR_STYLE_RULES, SCALAR_STYLE, dump } from 'js-yaml'

const scalarStyleRules = Object.values({
  ...DEFAULT_SCALAR_STYLE_RULES,

  doubleQuoteForInvisibles: layout => {
    if (layout.style === SCALAR_STYLE.PLAIN &&
        // Original regex, but without tab
        /[\x7F-\xA0\u2028\u2029\uFEFF\uFFFE\uFFFF]/.test(layout.node.value)) {
      layout.style = SCALAR_STYLE.DOUBLE_QUOTED
    }
  }
})

console.log(dump({ text: 'first line\n\tindented line\n' }, { scalarStyleRules }))
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Output (⇥ marks the tab character):

text: |
  first line
  ⇥indented line
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Loading this YAML restores the original string, including the tab and trailing line break.