Function $interpolate

lib/test/angular/1.8.0/angular.js:13947–14081

* @ngdoc service * @name $interpolate * @kind function * * @requires $parse * @requires $sce * * @description * * Compiles a string with markup into an interpolation function. This service is used by the * HTML ng.$compile $compile service fo

(text, mustHaveExpression, trustedContext, allOrNothing)

     * - `context`: evaluation context for all expressions embedded in the interpolated text
     */
    function $interpolate(text, mustHaveExpression, trustedContext, allOrNothing) {
      var contextAllowsConcatenation = trustedContext === $sce.URL || trustedContext === $sce.MEDIA_URL;

      // Provide a quick exit and simplified result function for text with no interpolation
      if (!text.length || text.indexOf(startSymbol) === -1) {
        if (mustHaveExpression) return;

        var unescapedText = unescapeText(text);
        if (contextAllowsConcatenation) {
          unescapedText = $sce.getTrusted(trustedContext, unescapedText);
        }
        var constantInterp = valueFn(unescapedText);
        constantInterp.exp = text;
        constantInterp.expressions = [];
        constantInterp.$$watchDelegate = constantWatchDelegate;

        return constantInterp;
      }

      allOrNothing = !!allOrNothing;
      var startIndex,
          endIndex,
          index = 0,
          expressions = [],
          parseFns,
          textLength = text.length,
          exp,
          concat = [],
          expressionPositions = [],
          singleExpression;


      while (index < textLength) {
        if (((startIndex = text.indexOf(startSymbol, index)) !== -1) &&
             ((endIndex = text.indexOf(endSymbol, startIndex + startSymbolLength)) !== -1)) {
          if (index !== startIndex) {
            concat.push(unescapeText(text.substring(index, startIndex)));
          }
          exp = text.substring(startIndex + startSymbolLength, endIndex);
          expressions.push(exp);
          index = endIndex + endSymbolLength;
          expressionPositions.push(concat.length);
          concat.push(''); // Placeholder that will get replaced with the evaluated expression.
        } else {
          // we did not find an interpolation, so we have to add the remainder to the separators array
          if (index !== textLength) {
            concat.push(unescapeText(text.substring(index)));
          }
          break;
        }
      }

      singleExpression = concat.length === 1 && expressionPositions.length === 1;
      // Intercept expression if we need to stringify concatenated inputs, which may be SCE trusted
      // objects rather than simple strings
      // (we don't modify the expression if the input consists of only a single trusted input)
      var interceptor = contextAllowsConcatenation && singleExpression ? undefined : parseStringifyInterceptor;
      parseFns = expressions.map(function(exp) { return $parse(exp, interceptor); });